It happens to me when I am not very focused or motivated in what I am doing that my thoughts fly to another place and like you I came to the conclusion that it is best to pay full attention to what we do or we will spend more time than necessary doing something, it has happened to me, so I should put more emphasis or concentration on focusing on the present moment, on what I do.
Exactly! And it happens to most people too. The first step to learn to focus on the present moment is to do simple meditation sessions: deep breathing through the nose and paying attention to the flow of air in and out...