Obey the Law of Three
Tracy's Law of Three holds that of everything you do, three tasks account for about ninety percent of your contribution. Identifying them is one of the most important things you can do for your productivity.
To find them, list all your work activities and ask three times: if I could do only one of these all day, which one would add the most value? The three answers you circle are your true job.
Once you know your three, resolve to work on them at your peak energy and to delegate, delay, or eliminate as much of the rest as you can. This is where quality of life and quantity of output meet.