Great question, and thanks for sharing your own strategies!

• Getting organized early is a big one for me. I have a really intense school binder setup with information listed redundantly throughout and on a wall calendar. I also download/buy/photocopy all the readings and put them in folders in my dropbox, organized by class and week.
• Prioritizing homework over going out, and giving myself permission to decline invitations in order to protect my mental energy.
• Reading for fun, not just cramming school reading.
• Letting myself have time off when I'm mentally exhausted, by watching tv or drawing or listening to podcasts.
• Joining a choir. I love to sing, and it's actually really good for you—there are studies that back me up on this! I took a one-credit choir course each term my last year of undergrad (except the semester in Ghana, when I took a dance course).