Worrying is hard on you.

I’m told that getting physical exercise is good for worrying because it burns off the stress hormones, which otherwise stay in your system and tend to cause you to ruminate.

Other than that it might also help to deliberately say a ressuring self-talk to yourself: make up a paragraph of reassuring statements that are relevant to your situation: “I will be okay. I can do okay at school. I will keep finding time to study. I will be okay, even if I fail a class. I have every chance to pass all my classes… ” That kind of a thing might help a little bit. Keep repeating it when the worrying comes back.

You could also try talking things over with someone to see if your worrying is realistic or not.