what evilchimp said is probably true for people like him or others.
but if the dude training you is your friend, he'll go all out to help you get better, even if you get better than him as well :]
I got trained by Groovy, known him since aaaages and at one point, i started to kick his ass around the map as well ;D , although you won't find many trustable people these days.
back to the point - if you really 'want' to be trained, get to a friend of yours who is better than you and ask him to train you, and if its a good friend, he'll go all out like I said.
-edit-
one thing lynx said is true about training screwing you up, but if the person training you is good, it'll only help you rather than screw you up.