It's just a phase.
...
Okay, I told you, now what?

But really, having less time makes you more efficient with your time. I used to find that during the school year, when I'd be in school 7-8 hours a day and doing homework for hours after that, I'd still manage to find several hours to practice every day, even though that was just about all the free time I had in the entire day.
But then over Christmas, spring, and summer breaks, I'd often only play a couple times a week. Losing all the structure to my life made me lazy with piano playing too. This summer, though, I've been playing hours and hours every day. Why this summer but not most summers?? Well, I think it's because the last couple summers I worked inconsistent evening shifts at a grocery store. It could be 4-9 Tuesday, 5-10:30 on Friday, noon to 6 on Saturday, 7-1 Sunday etc. I was doing something that took up a lot of my time, but it wasn't rigid. I still wasn't in a schedule. This summer, I'm working a desk job 8-5 weekdays. I'm in a rigid schedule, which I think is why I'm able to focus my energy better at the piano in my free time.
Basically, I wouldn't worry about this becoming a habit. As soon as school starts back up again, I'm sure you'll be able to find time to play the piano and become motivated again.