as Ambo said, running is great, put 20 mins aside and just go on a little run. All the stress you felt from classes get swept away since you're dialed in on running. Mental reset and go for the next day.
Another thing that helped me was always sleeping on time. I set a time of 11pm every single day. No matter what I had to do, if I had homework the next day. I would go to sleep because that's what's important.
The only time I broke this rule was last week of school when I had to finish some art projects and I stayed up. But every day before that, focus solely on the work and one 11 hits stop everything and sleep. Sleeps important and it's something you should have some control over.