If there is not good idea,

following advise might help.

• Study another thing hard, until you forget the anxiety

Enthusiasm may cure your bad feeling, and may give you a kind of satisfaction.
Note: Do not think it is meaningless. If You would not waste time, you would never feel better.

• get rid of TODOs

One thing which affects your mental health is you are so busy.
Busy life sometimes gives you a kind of accomplishment, but it would not continue for a long time. As stressed material breaks, you would be break in a sense.

• If the list above does not help, just sleep until you satisfy

Sleep heals your tiredness. You might say you were not tired, but more or less you need some rest, after finishing something.
Too much sleep makes you boring eventually, then you can re-start.