And as Justin Cook from Business Advice Free says in his post time management for people running a business:
"Try to study your time. This lets you know how interruptions take up your day and the common issues you need to solve right away. And as you know the average time you consume for these interruptions, you will be able to spend a few hours for the things on your to-do list."
In order to properly manage your time, you need to look after your wellbeing including making sure you get enough sleep.