This was fundamental to my zen practice. At a certain time in my life I felt overwhelmed and recognized that the same thoughts would repeat over and over in my mind. I started a simple meditation practice where when I woke up I would repeat "you are not your thoughts" as a mantra to shake myself free from the cycles.

Over time you can develop a mental state where you can watch the thoughts simply pass by as if watching a gentle stream water flowing by instead of being drowned in a rushing river of thoughts.