My main misfortune is taking too much on myself. Sometimes problem become more complex, then it seemed. Sometimes I just need to refuse to do work, but I don't... Work, studying, teaching, pet-projects and so eat my life. As the result, 24h is not enough,I'm not resting enough.
But there are some things help me to manage my time.
Google Calendar - the calendar for long time planing, scheduling and events with defined time. It helps me see my free time.
Notion.so Calendar - aka "Trello calendar". I have classic lists ( "todo", "doing") for tasks out of scheduling. And Notion helps manage those card-tasks in calendar.
When I need to do something I don't want to do, I use Tomato Planning method with Pomotroid application. It helps to concentrate and avoid procrastination.
And of course things everybody knows but nobody follows :)