Hey. I was out on disability for over a year and when I returned I was really nervous. But I did a couple of things to help:
1) I made sure I took a lunch break AWAY from the office to get out and clear my head. Sometimes I took a walk, sometimes I went to eat.

2) If you have an office, close your door a couple of times a day and take deep breaths. If you don't have an office, maybe try the bathroom or another place where you can just get 5 minutes to breath.

3) Don't volunteer to do "extra-work" in the beginning. Take time to get used to working again and just focus on your immediate tasks.

4) Talk with people at work. This help break up the day and the mood. Chit-chat about fun things.

5) Get enough sleep!!!!!!

These are what helped me back. Good luck. Take it easy.