What does the phrase “You don’t have to work 12 hours, you have to work with your head” mean?

This phrase means that you don't need to put in long hours of work in order to be successful. Instead, you need to use your intelligence and creativity to get the job done. It implies that smart work is more important than hard work. It suggests that you should use your brain power to find the best solutions to problems and to make the most of your time. It also implies that you should be strategic and think through the best approach to any task. By working with your head, you can be more efficient and get more done in less time.