I had a lot of trouble with this when I stopped working. Actually, that's why I am back in school, preparing for a new career at age 55.
It's a real problem for those of us who have always been "on the go." Eventually, I began to appreciate having nothing to do. The university work sort of comes in cycles; it's different than work stress. I still get bored on some days, even when I've taken a ride, gone to the gym, or done a lot of writing or reading.
I did some volunteer work for awhile, before I started my substitute job last winter. Is that a possibility?
I think one of the main issues is that I only have one friend who doesn't work, and I can only take her in short doses!