There is a fundamental strategic flaw in most writing about time management. That flaw is to suggest that better time management allows one to do more things.
It sounds logical. If we are more efficient in how we do things, we open up more slots in our daily planner, right? Sadly, the real world does not work this way. In the real world, becoming more efficient usually has two effects (1) you get sloppy about the effects and quality of what you do, and (2) you get opened up to more people making claims on your time.
In other words, you cannot win. That does not mean that time management is useless. To the contrary, we need to manage our time. We start by giving up the idea that we can have it all. We can only do a small percentage of the things that are possible. Time management will not change this. But it will help us prioritize which of these things we choose to focus on.