I used to be one of those happy people. It's not that I thought my work was great; quite the contrary. I knew I sucked, and knew I would always suck no matter how much I improve. But that knowledge made me happy. I delighted in knowing that I would never run out of room for improvement. The road before me would stretch on forever. How exciting is that?
Depression and anxiety turned that upside down. Now, instead of "look at how much I could improve from this point on!" I think "I'm not good enough." That's the key phrase, "not good enough." Those are the words of the devil. It's what anorexics hear when they look at their own bodies. I hear those words when I look at my own work. I've come to understand that my perception is seriously warped, and that's helped a ton, but I have a LONG way to go before I can be the happy person once again.
I don't put my art down, though. (at least, not for the comic.) It's my writing that my anxiety uses as a weapon.
So yeah, I've been on both sides of the fence.
Believe me, those who want that the most... are the miserable people themselves. Because who enjoys being miserable, really? (Some people enjoy COMPLAINING about how miserable they are, but that's something else entirely.)