My friend asked me, "How can I tell her to turn off that voice in her head, and go back to the way she was before?"
My answer was that this is something everyone in the arts has to go through, and then find their way out of it. Getting back to doing one's own work probably turns out to be a bit different for everyone.
It is easy to be guided by criticism. Even easier to be guided by praise! Children and old people, who are naturally more self-guided, and who come by their self centeredness in opposite ways, are the experts at doing their own thing regardless of others. For the rest of us who are past childhood but before the age of retirement, learning to tune out others is a skill. Experience definitely helps, with ignoring comments or learning to choose, cafeteria-style, the remarks that come your way, keeping the useful ones and letting go of the ones that don't help.
Putting your work in front of others initiates a chain reaction of judgement that is unreliable. The sooner a creative person accepts that , the better off he or she is, and the more willing to trust the inner impulse that has been guiding their creativity all along. Most viewers judge creative work based on what they like or dislike, or by price, and the ones who are elevated beyond that and perhaps coming from academia, the world of history and style, very often do the same---or they might judge things based on approval passed down by art historians before them, by friends or teachers whom they admire, or the fact that something hangs in a museum versus your art studio.
I don't think anyone is totally objective, but we have to try to be, because the effort reveals how difficult objectivity is, and the effort gives you a deeper understanding of the rarity of a searching, open mind that is willing to experience and judge without being first told what to think.
What I do varies. Sometimes I ask people what they think about things I'm working on, sometimes I don't, but when I DO ask, I'll ask anyone. The mailman, the pest control man, anyone who walks by. Other times I keep it all a big secret. Discouragement at the wrong time is bad. For instance, I would never ask the opinion of anyone on an unfinished work I was in the middle of, if I were happy with the way it was going. There is no point to that.
Opinions of others are best when you are :
Finished, as far you can see.
Stumped and wondering if you should throw it out.
Reasonably o.k. with your results but not thrilled.
Curious how it will strike the eye of someone else.
It's not about:
Am I good enough?
A creative person is required to be a cold-blooded judge of their own work, learning to bear the opinions of someone---for better or for worse--- and only being swayed by it if you believe it to be meaningful.
It's been my observation that a creative person who is on their genuine path is not too bothered by disparaging comments, maybe because enthusiasm is such an energy-maker. I think artists are thrown off track much more by praise. I think all the thumbs up on Facebook, the hundreds of thumbs up, every time someone posts a picture of their latest painting of this or that, have done more to distract artists in general than any number of "I don't like it" comments ever could !!
These days I think a side-effect of so very many artists teaching workshops is that artists are too often required to present themselves as experts, "modern masters", who voice opinions rather than ask for them. So asking a random person "What do you think of this?" is out of style right now. Your students might take the workshop from the artist next door if you show you are not the keeper of keys of all wisdom or whatever.
When my art studio was surrounded by other art studios, it was convenient to ask the opinion of others if I felt like it. In a pragmatic view I had narrowed it down to a few people whose eye offered something specific. For instance, one person had ten times my education, and another one had a really strong sense of composition, that kind of thing. Their comments were interesting. I can't remember being guided particularly by anything they said, the enlightening thing was that they often zeroed in on something I had noticed myself but didn't think anyone else would notice. They showed me what other people saw when they looked at my work.
It's been my observation that the most confident people are usually good listeners who don't silence opposing views or cry over them. The fact is, it doesn't really matter what other people think. It matters what you think. In every area a creative person has to learn to trust themselves. But if you don't put your work out there and be vulnerable, it's a loss, because there is so much to learn in the experience of doing that.