Welcome to psychcentral! imo What you are doing is a common cognitive distortion: all or none thinking. You probably see things in black or white categories? If your effort falls short of "perfect" you see yourself as a total failure, this causes a lot of anxiety!

Second guessing ourselves is a bad habit. Now you are even second guessing your thinking! Are you thinking "correctly?" ((((hugs))) Try spending a limited amount of time on something (give yourself a time limit!) Then stop. If the thought comes back, tell yourself STOP. Tell yourself that you already thought about that. Replacing your ongoing dialogue with some good stuff might help too!

Welcome, again! Hope this helps.
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