I think one of the biggest thing a trainee has to deal with during their formative years is criticism. You don't want to be noob who comes up through the lab and never has their ideas challenged (read shredded to pieces, incorporated into an effigy of oneself that is to be set on fire while the lab members dance around it and whack it with sticks). The first time you get that upbraiding by your PI or a committee it is going to suck. And its going to sting. But that's okay, it should sting, it means its working.
No one enjoys being criticized but it is so very important to the learning process. We challenge ideas everyday, if you cannot survive having your own challenged and don't have the ability to respond in a rational manner, you need to get out now. When I get criticized it literally feels like a sucker punch to the gut. Its the realization of I could have done better or should have thought about this or that. But to me that voice in the back of my head softly calls out, "Are you sure you should be doing this? Maybe you aren't cut out for this."
When faced with doubt and self-loathing you come to a serious fork in the road my friends, you either let it eat at you or you "sack the fukke" and do better next time. If you let it really dig at you, its just going to create this festering wound that just makes you a bitter person. I have seen this before as other trainees take the jab to the face, then turn all kamikaze and go out in flames. There is no glory in getting knocked out the game, you have to take the beating it makes you grow both personally and professionally.
Also, don't just brush aside this negative assessment of you as the rambling of fools or those that do not understand you or what you do. That's a perilous road to travel and probably someday you'll be whining about how fucked up the system is and how the deck is so stacked against you (Wahhhhh, but I need my A2!!!!!) over at Rock Talk.
So when you get cracked upside the head with the clue stick*, STFU and take your lumps. Learn from it and be a better person.
*h/t to Abel Pharmboy for my own intellectual ass kicking.