A proven simple technique is an ABC rating of your priorities. Mark the tasks on your to do list with "A's" if they are critical for your goals and simply must be be done that day (or else you face serious consequences).
"B's" are less urgent but still important tasks that you should start right after you are done with "A's". "C's" are "nice to do" things that you could do if you have any time left after "A's" and "C's". Those tasks can be safely moved to another day.