Well, the other thing is -- don't fight for your wallet. Your wallet can be replaced. Your life can't.
We do occasional knife training (with wooden knives, lol) in my aikido class, and if it's taught me anything at all, it's how one slip-up can be fatal. If someone shows me a knife and demands my wallet, I don't care how many knife disarms I've practiced, he can have it.
OTOH, if someone demands that I get into his car, I'm running if I can and fighting if I can't.