Also, maybe you need a story line or theme to follow instead of just drawing great pictures for great pictures' sakes.
That's pretty much what kept me from becoming angry, or overly frustrated the past five years at ANY drawing for my site. My patience has evolved to the point of where if I get a few lines into a picture, I'll know whether or not the picture is destined to be completed or to be tossed, so if I do waste a drawing I haven't put more than 20 minutes into it.
Another trick is to listen to some 'fun' music while drawing. I found putting on some headphones and listening to stuff like Ace of Base kills the "OHMYGODTHISHASTOABSOLUTELYPERFECTORELSE!!!!"-ness and makes creating a drawing something that's enjoyable, rather than a chore.