When doing problems, I am often in a daze, my head is numb and I can't concentrate. What should I do?

Let's see if it's a pathological reaction first

If not, you are in a bad state of mind. Please deal with things other than study first. Keep a stable and optimistic attitude. You will find that you will learn things quickly, feel particularly good and have a sense of accomplishment.

Give you some advice: more exercise will make you feel happy (with scientific basis)

Don't make life simple, for example, if you want to go to a familiar place, but you have to take a bus every time, you might as well try to walk or take a different route.

Do things in a planned way and don't let yourself think about things that will affect your temperament.

It's good to listen to music quietly. Wish you success!