Work Dreams

I recently found out that the person hired to fill my position when I left has already packed her bags and moved back to New England. The reasons I heard ranged from "overwhelmed" to "a complete disaster." This has sent me off on a new series of work dreams and late night anxiety about work. I thought when I quit my job that the job anxiety would quit with it. Instead, I've started worrying about my co-workers who have to pick up the slack for the missing position. I'm having dreams about being late to work and missing important meetings/training sessions. Why am I crazy?