Oh dear I have the same issue. I'm kind of afraid of not having free time. Isn't that weird? I haven't had a summer off in a long time and now that I have one, I'm just loving doing pretty much nothing. And that has got to be the saddest thing I've ever said.
But it's not just "nothing," I've been working on art and writing a novel and things of that nature. If you're the creative sort, I'd suggest taking the time to actually do some of those things because, Lord knows it's difficult to do when you have school going on.
I, too, need some motivation to get myself back to the gym though. So I say you and I--both of us--we just do it. We've got to kick ourselves in to shape and go for it. We're blessed with the opportunity of a free summer and we should use it to make sure we're carrying a little less weight for the Fall Semester.