You've been demoted. How did you handle the first day back in the office?

A friend of mine was demoted today, from a leadership position with direct reports to a regular employee. Has this ever happened to you and how did you handle it?

I think the first day back will be the hardest, and in this economy keeping your job, any job, is important. I feel bad about the situation, but should I? At least my friend is still employed, and I feel relieved in a way.