It may be possible to learn self defence without learning to fight and testing your skills, but your first test will be when you really need to defend yourself. You will not truly learn to defend yourself without full contact sparring and either tournament competition or street fighting. You can find that in San Shou, Judo, Thai Boxing, Western Boxing, Olympic Wrestling, full contact TKD, etc. A good exercise is to reach black belt level in a non contact system and then enter a full contact tournament. The first full power hook to the jaw or full velocity Judo throw to the floor can be a real eye opener.