I have pretty thick skin after some rather strong responses on a fanart piece I did a while back(the Dota 2 community is merciless about fanart). At first those comments were initially very ego bruising, but they ended up turning into rekindling my drive to improve.
I've been drawing seriously on and off since I was about 10-12 years old. My work has never really been seen as anything special, it's never been super horrible either, but no one has really encouraged me, other than myself and maybe one teacher. I'm in college now to be a graphic designer, however I'm unsure of if that's what I really want to do.
The books I've used to try to help myself further are Bridgeman's Life Drawing, Loomis' Successful Drawing(I really like Loomis), and a little bit of Perspective Made Easy. I currently have been working on perspective the last few weeks, since that was something I've never really worked on directly before.
Brutal and constructive honesty is what I want. I have been the driving force behind my desire to improve, I've found that I'm not as happy about praise as I am about someone pointing out a mistake I was blind to. =]