If there were only one job you could do at the highest level today and nothing else, what would that be and why?
If you can answer this question and then invest all your energy to complete this immaculately, even if it takes up 80% of your day, it will be your best investment for the day.
Chances are if you put 100% of your energy on this goal, you will find that you will complete this task much quicker giving you great energy to then continue that focus on other important areas during the day.
At the end of the day, it is not how much you complete, it is what you complete!