“What are you doing here? Thinking? And how can you go on thinking, thinking, thinking?… That’s the way to go out of your mind!”
Volodya by Anton Chekhov
The habit of excessive thinking may activate a special network of brain regions, called in neuroscience “Default mode network”. That means you endlessly chew over stories about yourself.
“Unlike other animals, human beings spend a lot of time thinking about what is not going on around them, contemplating events that happened in the past, might happen in the future, or will never happen at all. Indeed, “stimulus-independent thought” or “mind wandering” appears to be the brain’s default mode of operation. Although this ability is a remarkable evolutionary achievement that allows people to learn reason, and plan, it may have an emotional cost. Many philosophical and religious traditions teach that happiness is to be found by living in the moment, and practitioners are trained to resist mind wandering and “to be here now.” These traditions suggest that wandering mind is an unhappy mind.”
A Wandering Mind Is an Unhappy Mind by Matthew A. Killingsworth and Daniel T. Gilbert