Great question. My go-to thing is mediation and power-posing. There's aTED talk on power-posing and how it affects your mood and people's perception of you. You can look up Amy Cuddy and listen to her lecture. It'll only take 2 minutes and it works for me. For meditation, I do it for 5 minutes before I go to sleep. I tend to get really good sleep if I meditate right before.