Overthinking is an inaccurate term we mistakenly assume means we are complex thinkers. The better term is repetitive thinking; more like an OCD glitch in our programming. If we were truly overthinking, anything, then we would have a cure for cancer.
The average human has about 50 thoughts per minute; most of which we are unaware of storing, let alone identifying. So, when you ask someone what they are thinking and they say I do not know, they are not lying because we are unconscious of about 90% of those 50 thoughts. Worse yet, most of these thoughts are on replay. We tend to have a bad habit of repeating variations of the same thoughts for years.
Don Miguel Ruiz shared the Toltec belief which taught that this overcrowded thinking process, called the Mitote, "Is a thousand people talking at once while no one listens.” Akin to a ghost-like fog that blinds our path; deafens our ability to hear our own voice; and distracts us until we lose our focus and ourselves. Removing them will remove the chaos of the mind and replace it with clarity of mind.