It can be soooo frustrating at times, but when you move beyond a difficult area and realize that you just improved as an artist, right then and there, it's worth it! I may have to try 20 different things to get a nose to look right, or a skin texture to look right, but all that matters is that ONE time it works. Even creating something cartoony or comic-book like can be so fulfilling. It doesn't have to be a huge, epic piece of work.
Well, psychology will tell me that I experience something called "flow" when I'm drawing. It's when a person loses themselves completely in what they're doing, but is also challenged and completely enveloped in the activity. For me, I feel completely relaxed and find it to be a perfectly productive way to escape for a few hours. So drawing gives me great stress relief as well as a nice sense of worth and purpose Yay art!