Overthinking is always bad.Thingking is good or bad depends on types and ways of thinking. You have heard and read about thinkers. They are highly respecatable and what they had or have uttered are followed. But too much thinking is not appreciated. Why? because too much thinking or overhinking is detrimental for health. It causes depression, anxiety and creates problem for a person. It's said that women think too much but it's not true.
The link between overthinking and mental health problems is a chicken-or-egg type question. Overthinking is linked to several psychological problems.
The more you think, the worse you feel. And your feelings of misery, anxiety, or anger may cloud your judgment and prevent you from taking positive action. When you start thing too much about problem it increase your anxiety however if you think about solution of the problem, it does not affect you negatively, rather, it opens several avenues to come out of the maze of problems.
Time spent developing creative solutions or learning from your behavior is productive. But time spent overthinking, whether it's 10 minutes or 10 hours, won't enhance your life, rather, it reduces your reasoning power as well as causes weakness in body. Some people are involved to swim into ocean of imagination. They think about those things which are inaccessible to them. They think about celebrities, movie stars and world class players. They keep them closer or have close relationship with them in imaginations. They create their own world where they are the most powerful people. Their popularity is beyond attainability even for all humans but they achieve everything in imagination. It's waste of time.