Creatives are notorious for being unsatisfied with their work and for that translating to a general unhappiness in life. Hidden in that, though, is a real key to creativity, as long as one can find the proper balance.
I think Simon Cade from DSLRgude is spot on when he talks about "constructive pessimism" and moments of brilliance in this video. There's a certain mysticism around the creative process, as if it's a magical thing during which the artistic genius conjures flashes of inspiration, when anyone who works as a creative knows that those "flashes" are really the sum of decades of learning, experimentation, refinement, repetition, success, and failure, and when seen that way, they're not magic at all; they're hard-earned. Of course, the downside is the feeling of never being good enough and never being ready to release one's work, because it can always be better. As a composer, I struggle with this constantly. There's no piece of music I've put out that I haven't thought "that transition could have been smoother, that chord voicing could have be clearer." It's a difficult balance both to find success and to be happy with ourselves and what we do, and I suspect the balance is different for all of us. Do you struggle with it? Let me know in the comments.