It is not enough to know what is important and what are the priorities. You also need to know how long it would take to complete a task – how much time you would have to devote to them. Therefore, when preparing your to-do list, add a column where you mention the estimated time each task should take and an adjacent column with the cumulative total.

Then do a simple time study. As you do each task, write down what you did and the start and end times. Keep track for an entire day. Then repeat it a couple weeks later on a different day. It isn’t an exhaustive survey by any measurement, but it will give you some insight. If you work 10 hours a day, you will notice that the important tasks on your list require only four hours which gives you remaining six hours for other tasks. If you feel that much of your day is taken up by interruptions – dealing with events that happened, crises that came up, or problems that had to be solved,  then on average these interruptions consumed four hours a day, you still have six hours a day for the things on your to do list.

Each night, before you leave the office or before you go to bed, update your to do list. Delete the things that you have completed, delegated, or downgraded, add the new things that had come up, rearrange the priorities to get the most important tasks on top, and assign estimated time to each. Then go down the list to the six hour mark and draw a line. That becomes your target for the next day.