I think you have to keep going at it and every time you learn something new then, the next time you are working on a model and you just do that thing you think, wow I actually learnt something! It might help to stand back from your model and think last week I could not have done that, not, wow someone else would have done that better.
I'd recommend starting with some tutorials- the ones on this site are excellent and I learnt some jolly things from them. I bought a couple of books as well. I'm sure some people can just pick up modelling from messsing about with the programme, but I have found the structure of tutorials helpful myself.
I look at other peoples work and think I can't do that now, I may never do that, but I'm going to keep trying to improve. Maya is an incredibly complex programme; you can't master it overnight. I doubt, as it is a hobby thing for me and I don't have time to do much with it but dabble, that I will ever master it, but as long as every model is a teeny bit better than the last or does something new, that's enough for me. I don't have any aspirations to do this for a living though.
Finding a forum where experienced people are willing to help is a real bonus I think. The other forums I have visited tend to have a lot of people who are intolerant of total noobies and people that ask questions and indeed amateurs- thats not the case here at all and that's really great I think. I have also found the challenges useful to focus on something to model.
Modelling is just like web spinning though for me- if at first, second and third you don't succeed, try try again. After all hidden in everyones maya folder are some things they would rather forget too