"Off days" are a part of life, I guess, whether you're a cartoonist, a neurosurgeon, or an air-traffic controller.
As a kid, I knew I wanted to be either a cartoonist or an astronaut. The latter was never much of a possibility, as I don't even like riding in elevators. - Bill Watterson
And remember whatever discipline you're in, whether you're a musician or a photographer, fine artist or a cartoonist, writer, a dancer, a singer, a designer... whatever you do, you have a thing that's unique. You have the ability to make art. - Neil Gaiman