Just a quick observation and I know you all might hate me for saying this ... but being bulletproof implies that you don't let anything affect you ... then how will you allow yourself to be affected when it is the right thing to be doing?
I mean should we not all take good constructive advice on board and let our emotions come to terms with the fact that we have struggled to improve?
Actually I agree with this, the bulletproof theory is great as just that, a theory. If we make our entire persona completely bulletproof then we also deprive ourselves of feelings and empathy becoming numb ourselves because there is no picking or choosing moments to bring the bulletproof-ness out, it becomes a permanent aspect of our overall personality.
I know this because I know of a few 'bulletproof' people, both men and women, and they generally come across as very cold and uncompromising, to everybody! that's the thing, why alter our entire personality to combat criticism? I see that as punishing ourselves.