Back in high school, my mother taught me how to plan any project or study that I needed to do. I’m a terrible procrastinator and it wasn't difficult to draw up a plan and it didn't take much time. When I divided my work into small parts, it was much easier for me to work with this later and I didn't lose my thought, so I got good essays and studies. You need to try this method, if it doesn’t work, then there are many tips on the Internet on how to organize your day, to be effective, to evenly distribute the time between work and rest. I wish you good luck with your doctoral work!