Well I can tell you what works for me.
Step 1. Step away from SDN
Step 2. Remove yourself from all neurotics who are tweaking out over medical school
Step 3. Sex.
Sadly, this only works with acute onsets of burn out. For more chronic cases you'll need to do the following.
Step 1: Remove yourself from SDN, all gunner types, and tell your family to come up with different questions on the phone. "How is school/What are your grades like?" is just going to give you problems.
Step 2: Schedule time for yourself. Just you. Then actually give yourself that time on a daily or every other day basis. Whatever you can spare, even just an hour.
Step 3: Use that time to first recover yourself physically. It may be affecting you mentally if you haven't gotten enough sleep, eaten fruits and vegetables, or stretched your legs. Recover. Not with comfort food, not with beer, with good nutritious stuff. You're going to become strong again.
Step 4: Feeling a little better? Now take that scheduled time for yourself and pursue something new. Specifically something that exercises your mind in ways that it isn't getting in your science classes. For me that was strenuous physical activity or playing music, the only things that actually get my brain to SHUT UP. Exercise a new kind of intellect.
Vacations are nice if you can take them, but it doesn't change the environment that is burning you out. If you don't want to get burned out when you come back, you have to make your emotional well being a priority. Even over other people, even over being the perfect premed.
