The Calvin and Hobbes cartoon from December 13, 1995 made a big impression on me. It's been on my wall since I cut it out of a newspaper that day.
First panel: Calvin is standing in front of a large pile of snowballs. He raises his arms triumphantly.
With 200 snowballs at my immediate disposal, I have no opposition! My will is law! I am omnipotent!
Second panel: Calvin stands there with his hands on his hips, staring straight ahead and grinning wickedly.
Third panel: Calvin's hands are behind his back. He's still looking ahead for any potential adversaries, but his face now bears a thoughtful, quizzical expression.
Fourth panel: Calvin turns toward the audience. Arms hanging straight down at his sides, he states candidly:
Bill Watterson, the strip's author, retired at the end of that year. He was the acknowledged master of his art, but wise enough to know to look for new challenges.