Myth 11: getting better at winning fights is the highest (and indeed only) goal of and reason for martial arts training.
This assumption seems to be gaining ground among MMA fans and streetfighting fundamentalists.
'What's the point of learning foo-do? I saw a foo-do expert go up against a BJJ expert and he got his ass whupped.'
And it's complete rubbish. I've been practising various martial arts for a few years now and I've gained a lot. I'm fitter and healthier. I'm better balanced and if I do fall over, I'm more likely to roll out of it and less likely to injure myself - I can't quote any statistics, but given how seldom people actually get into unavoidable fights, I'm pretty sure that this is more likely to save my life and limb than having l33t fighting skills. I'm better at keeping my head when things start going tits up. My reactions have improved. I've learnt interesting things about eastern philosophy and applied anatomy (namely, how joints do and do not bend.) I've had the satisfaction of learning to do something difficult. And, shameful though it is to admit it, I've had fun.
So yeah. I'm not quibbling with Ashenai's points. There's nothing more dangerous than teaching someone a couple of impractical techniques and then telling them that they're invincible and should go and pick a fight on the next street corner. But if you keep that in mind - and a lot of martial arts put heavy emphasis on learning to keep your head and resolve a conflict nonviolently - then you can get a hell of a lot more out of your training than just being the biggest asskicker on your block.