If you find it difficult to laugh, think of your favorite song and start humming it for a while. Doing this can put a break to your stress cycle for some time.
As per Don Campbell, author of the Mozart Effect series, musical humming improves health. Humming relaxes tensed muscles, improves mood, blocks racing thoughts in the head, and helps in breathing more deeply. If you’re stressed, this sounds like something you need to try out!