It's difficult, but certainly not impossible. I was a D1 athlete all 4 years of college and came away with a decent GPA but not great (3.5ish).
I had student-athlete friends who were 3.7+ though (usually in non-science majors however).
Time management is crucial. Take advantage of any gaps in class and practice time to study or volunteer for a couple hours rather than nap. This can be hard considering most programs have practice/training in the morning before class and in the afternoon afterwards and sleep can be a hot commodity.
The next best piece of advice I have is use the weekends to your advantage. Catch up with classes, ECs, or whatever else you can find time for. Once again this can be hard since competitions often fall on the weekend but try to take advantage of every free saturday and sunday you can get. Good Luck!
EDIT: Oh and one more thing. Study while you travel!! Studying during plane rides and bus rides can be annoying but it's better than just wasting that time.