[mrdependable]

Sheer force of will. After working at a computer all day, sitting at a computer and working late into the night is the last thing I want to do. Thinking of the alternative, which is spending my life working for someone else, is my main motivator. I can't see myself doing that forever, and I know things won't change unless I put in the work. So I do my day job from 9 - 5, hang out with the family from 6 - 9, then work until 2am.

[itamarst]

As I mentioned in another comment, you can negotiate a shorter workweek. I've done it, others have as well - see link in my other comment.