You don’t need more time management.
You need to say “No” more.
I watched an interview with Elizabeth Gilbert recently. She said “When I was young I used to think that if I said No to people, they would feel rejected, get angry and feel let down. Now that I am older I realise that when I say No to people they do feel rejected, get angry and feel let down… but I have to do it for me.” It is true. It is not easy to say “No”.
Dharmesh Shah gives a good thought on framing your “No”.
It’s not easy.