Don't be used by it
Humans who overthink loose their sense of reality, they go through possibilities, outcomes and illusions over ams over in their heads. Overthinking causes them to feel insecure, to question everything and to have no confidence in the present moment. If you'r struggling with overthinking, jist remember that thinking is a tool. Tools are meant to be used.
You are not your thoughts, use thinking, don't let thinking use you