There’s nothing wrong with anticipating the consequences of actions and choices. The ability to do that has been a huge evolutionary boon to humans. It keeps us from doing crazy shit. That’s not what “overthinking” means to me.
Overthinking, in my book, is unnecessarily complicating things. Very often intuition is a more efficient guide than thinking, because it doesn’t get bogged down in complication; it’s fast and economical. Sometimes you just “know” how to proceed, without necessarily being able to explain how you know. If you’re good at tuning into that intuition and trust it, things can go amazingly smoothly. This is what some call the “flow” experience. Thinking just gets in the way.
But intuition doesn’t function well in all situations. There are plenty of times when it will lead to wrong conclusions, and only careful thought, as cumbersome as it may be, will show the way. The essential thing is to understand where intuition’s weaknesses are.