Why did Bill Watterson stop writing Calvin and Hobbes?

Bill Watterson ended Calvin and Hobbes when he felt like he wanted to pursue other endeavors in his life. The final cartoon of Calvin and Hobbes is him heading out with his toboggan into a white snowy field and saying "Its a magical world, Hobbes, ole Buddy, lets go exploring" which summed up what was going through Bill's mind. This was one of the most popular comics in his series.

AnswerWatterson has said that after ten years of keeping his artistic creations to small little panels, he wanted to explore larger expressions of his painting desires. He remains, as of May 2008, secluded from the public where he paints.