For me, a real confidence breaker is when I post art and NO ONE comments on it. They may look at it, but no one makes a comment. I “used” to get this very frequently. Even if I asked and practically begged for constructive critisism, none was given. For me, that was a real confidence breaker and because of that, I nearly gave up posting my work anywhere because I felt that no one gave a crap about my work.
I mean, how can an artist better themselves if no one is willing to even say anything “in a nice way” on how you can improve?
But then I went to DeviantArt. I thought, “Why not?” So I began posting work there.
I’m VERY glad I did! Now, when people look at my work I will know if they like it or not. They favorite my work a lot. They may not comment very much, but they put my work in their favorites list. I always get notifications on that. I do get comments too, which is always nice.
So, DA has been a real confidence booster, at least for me. I still don’t get the constructive critisism I want, though. So, I try and get my hands on any useful tutorials and help me improve.
1. So…Tutorials! Search for any that your interested in. Learn them, memorize them, use them.
2. If you don’t already, get a DA account and start posting your work. Join some groups that appeal to you and post your work there so you get better exposure, get more favorites and more comments.
3. If your going for ultra-realism, get the Reality plug-in for Daz Studio. That’s an absolute must.
4. If your not into ultra-realism, get a tablet PC and learn how to use that. Learn how to paint using your favorite 2D program and turn your art into fantastic pieces people can gawk at all day.
You don’t have to do any of the above suggestions. They are just that…suggestions. I do highly recommend you at least get a DA account though. For me, it’s a confidence booster. It may not be for everyone, so go out there and see what can be your confidence booster. 
Good luck! 