There's a Dilbert cartoon that I had pinned up to my cubicle. In the first panel, Catbert walks up to Alice in her cubicle and says "You think you're satisfied with your job." Next panel, he's pointing at her and yelling, "In reality, you're just afraid of change!" Next panel, Catbert walks away, purring and thinking, "That was some of my best work."
How many people stay at lousy jobs because they're afraid of what the next job will be? I know I do.