Personally, my life drawing class was awful at first, and I felt like I was crap and doing horribly, until I managed to break my internal barriers about it.

...It might also have helped, though, that we learned gestures and the underlying structure of the body, and while my teacher was a tough old cuss who wouldn't praise you until you really deserved it, neither would he cut you down without then saying "now, to do it correctly, you need to do this and this, or possibly this..."

It can help to learn the rendering, though. If you know how to render it, ostensibly you're also figuring out what goes where and why. I've slid riiiight back into my own comicky style, but I still block out the proportions before I do anything and I think I picked up enough to save myself from horrible messes like my giraffe-neck phase and my everyone's-a-Barbie-doll phase.

So, I guess what I'm saying is don't give up? It takes a while for everything to settle right in the brainmeats, and it can be really frustrating until then.