This may sound like a silly thing, but I have a trick I can use when I'm buried in bed and just don't want to move a single muscle, much less get up. First, I ban all thoughts of what I have to do after I get up, and just focus on getting my body in motion. I figure I can handle moving one finger, so I do, then my hand, then my arm, and so on, until my whole body is stretching in bed. Kind of a reverse muscle relaxation. It may sound silly, but it gets me up and in motion, and you know the physics law: a body in motion tends to stay in motion.