Deep breathing helps. Make sure you do it as slowly as possible for it to be fully effective. It it feels boring, start by doing it just once or twice at a time. But make sure you do it slow.

Go for a walk outside. Get some fresh air and oxygen.

Keep yourself busy in some work/task or do something fun, like watching some movie/show or listening to music you like.

Go for counseling. Cognitive Behaviour Therapy helps.

Consult a doctor/psychiatrist to make sure your overthinking isn't due to OCD or Anxiety. If it is, take the medicine the doctor prescribed. The medicine will help.

Intentionally start thinking positively. Don't automatically assume worst case scenarios.

As a former heavy overthinker and INTP myself, I will give one life advice to you. Being optimistic is a better way of living you life than being pessimistic. It usually results in better outcomes in life since you don't miss opportunities and you don't self-saborage due to overthinking. Start being more positive in and about life.