The worst feeling I think any artist must feel (at least me) would be feeling that their work is unappreciated. Now, I'm not one expecting thousands of "likes" or favorites, but there's that certain feeling when you spend hours/days on something only to have, say, 3 views. I don't feel what I draw is bad, but it starts getting to a person when a famous actor or talent on, say, Facebook, posts that they sneezed and suddenly 10,000 people comment in their post. If I saw even 1/100 that reaction to things I made, perhaps I'd be far more motivated to draw regularly. Such is the fate of an artist, I suppose