the best self defense is to learn not to be in the wrong place at the wrong time, which usually involves bars.
I used to fancy myself pretty tough (over 40 years ago), and one night took on a whole gang of townies at once, one of whom sufficed to whomp me silly. It helped him that I was totally drunk.
I decided after that, fighting was not a macho game, but a serious affair to be engaged in only when necessary. That was my last fight, 40 years ago.
After that I was a meat lugger for a few years and became much stronger than before, but never fought. my friends at the meat market carried knives and guns and fought regularly, and even died. actually i seldom got challenged anymore in my end of town. for my friends it was different.
ill tell you anyone who got in a fight with one of them, martial arts or not, was in for a serious experience. but they also fought only when attacked since they knew the consequences. my boss once singlehandedly defeated 7 men armed with meat hooks and irons, and threw them down the stairs for trying to smash up his place for business competition reasons.
i also have a friend who was a martial arts champion, but it just caused him to be more and more bold in seeking fights, until finally a large gang of opponents beat him silly.
there is a little book i read my kids on the subject for children called "a bundle of sticks".
There is a scene in there where a rough crude guy in a truck opens his door into one of the good guys cars at a drive in and then complains to the victim about his clumsiness in being in the way of the door, and offers to fight him.
the good guy (a martial arts instructor) calmly points out that the big guy is fat and out of shape and that his friend smokes cigarettes, and that probably they do not really want to start a fight. so why don't they all just go inside and eat their burgers.
the two blokes in the truck look at him like he's nuts, but don't fight. then the good guy leads the student inside for a burger.
i guess the moral of the story is that it does help ones confidence to know martial arts or to be strong, but the real lesson is not to fight unless attacked. so the guy who ran at every sign of a fight was very wise.
my friend "big man", a 300 pound lugger who carried a knife and a gun, and who loved a good fight, went to prison for 10 years for killing some idiots with his knife who attacked him, and subsequently got so out of shape in prison he died of a heart attack.
i loved him, and he was a good man, but hanging out in bars and fighting the morons you meet there ultimately killed him.
read sometime the autobiography of malcolm x who realized in his job as a railroad porter that he could defeat an opponent just with his brains. or if you really want to get on another level, read the bible about what hapened when saul sent soldiers to capture david while he was living with the prophet samuel.
when the armed soldiers vcame near the camp of samuel, they laid down their spears and sang hymns and praised god. even saul himself had the same experience when frustrated he went himself.
there are many "fights" in life, street thugs are the easiest to avoid, at least once you get out of public high school in certain parts of the US. The methods needed vary, in fighting with administrators, dishonest politicians, or police, unscrupulous business people. There are certain methods that work in more situations than others and those should be learned as soon as possible.
notice the subtitle of the original works on judo by jigoro kano, is "the art of yielding".