“If you are trying to be focused and “productive” for more than 30 hours a week, you are probably working too hard. You should consider reducing your workload to become more effective and get more done.”
“To avoid wasted work, you must allow time to observe the effects of what you are doing, reflect on the things that you see, and change your behavior accordingly.”
“You need to spend evenings, weekends, and holidays educating yourself; therefore, you cannot spend your evenings, weekends, and holidays working overtime on your current project. Do you really expect brain surgeons to perform surgery 60 hours a week, or pilots to fly 60 hours a week? Of course not: preparation and education are an essential part of their profession.”
Olve Maudal 97 Things Every Programmer Should Know