Thinking is like breathing. We do it pretty much all the time, automatically. We can only exert so much conscious control over it. We can put it on hold for a short time, but the moment we stop paying attention it starts to happen again. Its quality and rhythm are influenced by our habits and emotional state. We even do it while we sleep.
You can do exercises to hold your breath longer, to control it more consciously, to improve its quality and function. Likewise with thinking.
The quality of your breath is how well it enriches your body. The quality of your thinking is how well it enriches your life.