We underestimate our mind wandering; according to Jonathan Schooler of UC, Santa Barbara, we think our minds are wandering about 10% of the time, when it is actually much more. In normal every day activities our mind is wandering up to 30% of the time, and in some cases, for instance when driving on an uncrowded highway, it might be as high as 70%.

https://www.blog.theteamw.com/2010/08/03/100-things-you-should-know-about-people-39-your-mind-wanders-30-of-the-time/