Taking an interest in self-defense involves several axes of development. On the one hand, develop physical (technical skills, physical condition… ) and psychic (management of emotions and stress, strengthening of the mind… ) and on the other hand, develop daily habits and behavior that allow, at best to avoid any situation of aggression, or at worst to deal with it as effectively as possible.
The choice of clothes to wear is part of these daily habits. Everyone dresses as they want, the clothes we wear are also a way to express our personality. In the case of a professional activity involving the wearing of specific outfit, the question of choice does not seem to arise. However, whether or not one is free to wear the clothing one wishes, a person who is interested in self-defense must keep in mind that in the case of an assault situation the clothes that we wear can weigh in the balance positively or negatively for the outcome of the confrontation.
A digression about martial arts outfits
Before continuing with this topic, I would like to speak about martial arts outfits. From the kimono of Judo, through the rashguard of MMA, to the abadá of Capoeira, the clothes worn by martial arts and combat sports practitioners seem to be specific to the martial techniques used. However, most of the traditional martial arts outfits come from clothes that were worn in old times, more or less distant, and which were not clothes intended specifically for a martial practice.
In Japanese martial arts, practitioners wear the keikogi 稽古 着, usualy called the kimono 着 物, and sometimes add the hakama in certain disciplines such as Aikido or Kendo for example. At their origin, these clothes are not for the training, but of everyday life clothes that the Japanese wore in the feudal era. The kimono was the most common garment and the hakama was worn by the samurai of which certain Japanese martial arts are the direct heirs.
The same is true for most of the Chinese martial arts. For Wing Chun in the old days, there was not really a specific training outfit. Ip Man was probably the first to introduce a dress code that many practitioners still abide by today. Most often, his students wore a white t-shirt and black pants. Ip Man used to wear a tangzhuang ; a jacket popularized in the Qing era that most men in society wore. In the photo below, the advanced students of Ip Man, seated by his side according to tradition, also wore the tangzhuang.
I will write a more detailed post on the outfits worn by Wing Chun’s practitioners.
In the Philippines, FMA practitioners sometimes wear traditional Philippine clothing or Japanese-inspired kimono-style clothing. Others on the contrary do not wear any particular clothing. When I practiced with Maestro Rodrigo Maranga, he wore most of the time baggy shorts, a t-shirt with the CEM logo, his Esrkima style, and sneakers because we practiced on hard ground.
In addition, some more modern systems such as Krav Maga or Jeet Kune Do often recommend an adequate sports outfit, such as sportswear (pants and t-shirt/sweatshirt), allowing mobility and ease of movement. Others also encourage to practice with “everyday cary clothes”, dressed in jeans for example, unisex clothing worn by anyone and which therefore joins the initial question of this post.
What are the criteria for choosing a garment …
Most of us choose our clothes according to our own criteria and the use we want to make of our clothes. The criteria most often used are comfort, quality, resistance, functionality, adaptability, good look, dress code …
In an assault situation, the two instinctive responses that come our way to face this threat are fight and flight. A communication time can take place before one of these two responses, but if you have to fight or run, it is better to have suitable clothing to do so. The authors of Protegor  give details on the criteria for selecting a garment which breaks down into four characteristics : technicality (thermoregulation, impermeability, insulation, etc.), ease (comfort, lightness, good mobility, etc.), resistance (quality of the garment, reinforcement area, solidity of seams, etc.) and look (to go unnoticed and feel good).
… based on the concept of self-defense?
So here are some tips and tricks for dressing in everyday life, keeping in mind that if we have to face an assault situation, the clothes worn will not be a constraint but an asset.
Feet. First of all, you should have shoes that allow you to have a good grip, stability, flexibility and protection, whether for fighting or running. The shoes can be used as a striking tool in self-defense situations and it is difficult to do a sprint in heels or flip flops ! A friend of mine, a Wing Chun practitioner, found himself in trouble during a tense verbal exchange with potential attackers while he was wearing crocs. He realized instantly that if the situation escalated further he was unable to defend himself effectively or even flee. Fortunately for him, he was able to resolve this conflict through communication, but this anecdote was a good lesson for him. For my part, I sometimes wear light shoes in summer (filp flops type) only if I am not far from home, in “known territory”, or at the beach. When I have to travel a longer distance in town, I put on suitable shoes.
Legs. You need a garment that allows you to move easily. I always make sure that I can do my movements and that I have enough comfort before buying pants. So I systematically test my kicks and low postures in the changing rooms because I think it would be really unfortunate if a martial arts practitioner could not use this or that technique because of clothing preventing it from moving properly.
A belt can also be a good accessory depending on the situation. A leather belt with a metal buckle can become an interesting defense weapon to keep an aggressor at bay by spinning it in the air or in the shape of an 8 in front. Of course, you still have to have time to extract it from the pants, the space to use it and take care not to lose your trousers !
Upper body. As with the legs, the priority is to move easily. That is to say being able to do gestures of great amplitude without being bothered by the clothing. Generally, garments with closure pockets are recommended. The zippers are the most suitable, buttons are also useful, first of all to protect your papers, your keys, your phone … it is more difficult for a pickpocket to access pockets when they are closed, even better in the case of internal pockets, such as inside a jacket. On the other hand, if we have to do particular movements of large amplitudes (races, jump, roll, movement on the ground …) this allows us not to lose these valuables.
Neck. You have to be careful with the accessories that stick out and hang… wearing a tie can be a disadvantage in a brawl because it can be easily grabbed. It must be removed in areas of distrust. The same goes for necklaces and long pendants, they can be introduced under a garment if necessary.
Silat’s practitioners will appreciate scarves which can prove useful in self-defense situations. However, the techniques used with this type of accessory are not within everyone’s reach, adequate and regular training is necessary to perform efficient actions.
Face and Head. Hat, hood, sunglasses, can be interesting if you need to cover up your face or avoid meeting the eyes of bad people.
About this topic, Rory Miller has highlighted that a situation of aggression in the street is declined by a ritual of domination with very specific steps, which he roughly calls Monkey Dance. The first of these steps is eye contact (often aggressive) and indeed hiding your eyes with an accessory can be a good asset in the urban jungle. The other stages are the verbal challenge, close the distance, the first physical contact (poke finger, pushing of the torso…), which leads to the last step ; the assault itself, the exchange of blows. 
I invite you to watch the music video La Bagarre, by rapper Kamini which is a good parody of what a Monkey Dance can be.
For the earphones, I’m divided. On the one hand they allow to put a certain social distance because people will not dare to approach someone isolated with his music in the ears, and from this point of view, it can avoid the verbal challenge according to the ritual of Monkey Dance. But on the other hand, earphones necessarily lower our auditory alertness and can allow a predator to choose us rather than another person.
At last for bags, it is better to have free hands and to avoid handbags, rather favor backpacks or failing that, shoulder bags (not ideal however because if you have to make large movements this can generate an imbalance, especially if the load is heavy).
The Grey Man concept
The “Grey Man” or “the Chameleon Man” is a concept of attitude and behavior aimed at discretion. Become an ordinary person, transparent in a crowd, using a rather neutral colorimetric outfit (grey, black). This involves avoiding attention-grabbing clothing, inciting distrust and belonging to a group. 
The Grey Man concept can appear very limiting concerning look and freedom of dress. It is an interesting concept but everyone must qualify it according to their personal aspirations and convictions. For who interesting to self-defense, it is necessary to know how to adapt and to be aware that violence happens in a specific place, at a specific time and between people. 
We must be aware of what we can and cannot do with the clothes we wear. This is essential for a martial arts practitioner aware of self-defense.
In this post, I have deliberately made no distinction between female and male clothing. Everyone will recognize themselves. Everyone interested in self-defense adjusts their clothing according to their beliefs and concerns. No dress code justifies being assaulted, everyone is free to dress as he/she wishes. However, concerning women self-defense, I still regularly see promotional videos/pictures staged where women dressed in sexy fashion defend themselves remarkably well against an equally stereotypical aggressor. From my point of view, these staged pictures are stereotypes sexist and aberrant.
40 years separate these two photographs which deal with the same theme ; women self-defense. Old stereotypes die hard.
These kind of images nevertheless arouse my curiosity and lead me to wonder :
Is wearing a skirt a vector of aggression ? Are “non-sexy” women safe from assault ? Do you have to be sexy to defend yourself effectively ? Do heeled shoes provide good stability for kicking or sprinting ? How easy is it to keep your self-control and defend yourself against an unexpected threat? … I could take the mockery further, but I stop here with my ironic questions.
For now, it’s time to sort through your dressing !
 Protegor – Guide pratique de sécurité personnelle, self-défense et survie urbaine, p68, MOREL Guillaume and BOUAMMACHE Frédéric, AMPHORA, 2017
 Meditations on Violence, A Comparaison of Martial Arts Training & Real World Violence, p42, MILLER Rory, YMAA Publication Center, 2008 and Facing Violence – Preparing for the Unexpected, p26, MILLER Rory, YMAA Publication Center, 2011