Head over and read a new entry over at Animator Island and read Tips for Drawing: Bad Days Happen. I often get frustrated when I have a bad day and just can't get the look I'm going for. If I'm animating, painting, sketching or any of the creative outlets I pursue the one thing that stays constant is that some days I fight to do it. I recently came to the realization that the best part about making art is when you can see it in your head and everything you try looks nothing like it.
Now that I gave you a quote I might as well give you a few more to drive the idea home.
"Even when you're experienced, it doesn't come easy & it shouldnt come easy if it comes easy then youre not doing it right." Malcolm Gladwell
“We all have 10,000 bad drawings in us. The sooner we get them out the better.” Walt Stanchfield