The Cleveland Plain Dealer, still one of the best newspaper names of all time, has an interview with Bill Watterson, the creator of Calvin and Hobbes, still one of the best newspaper comic strips of all time. There are links to his earlier work as a political cartoonist in Cleveland, and scanning through them I would have to say he really hit his stride when he produced Calvin and Hobbes. He has no regrets about retiring and is happy with a quiet life out of the limelight.
At the time, I was seriously bummed by departure of Watterson and Gary Larson, who created The Far Side, but I respect them for having pride in their work and knowing when they were pretty much out of new ideas. The generation of cartoonists previous to them tended to give up on cartooning when the pen was pried from their cold, dead hands, but the baby boomers had a bunch of guys who decided to move on when they felt they had produced their best work and continuing would just be a slow downward spiral. I remember when Berke Breathed came back after he closed down Bloom County, promising something new with Outland, declaring that he would do a new strip without leaning on the crutch that was his most popular character, Opus the Penguin. Readers of comics know how that story ended.