It's all about prioritizing.
Figure out how much work you need to put in for your classes. Do that.
Figure out how much volunteering/research/work/whatever you can handle that semester. Do that.
If you have room for other things you enjoy like performing or clubs or intramurals or whatever, go for it.
But at the end of the day, make sure you spend time with the people who are important to you. I know there were times in college when my friends didn't see much of me, but I knew if I didn't see them at all, I would go nuts.
Basically, don't sacrifice people for school. Remember, people are the whole reason we're going into medicine.