Artists are a fragile lot, generally. We begin from scratch and build our talents up, quite commonly starting at a young age when the most important thing is our parents' approval and our identities are still forming. I don't know about you, but I was really sensitive about my art at a younger age. I was particularly sensitive to criticism. Every good artist knows that (constructive) criticism is key to improving your own artwork, and that listening to what other people have to say about your stuff is essential to getting better. It's not easy to have the flaws pointed out in something you poured your heart into, that you spent hours on, but without criticism you're making the process of removing those flaws much slower. Sometimes you just need another pair of eyes.