4 hours a day, 4 days a week.
[This is something that's working well with me. So I think it might help you too.]
Let's start with the problem...
I have been struggling with this question for years now.
How long does a professional work in a day?
The industrial era has a straightforward answer - 8 hours a day, 5 days a week.
But that never worked with me. It always sucks me into tasks and chores energy (actually what it was designed for).
So, I tried a system that's been working well for me: 4 hours a day, 4 days a week.
Anything more is a bonus.
But if I get in these hours, I get more done in a week than otherwise.
I do this by setting a 4-hour timer on my phone when I reach the office (or cafe) and working until it goes off. Nothing more complicated.
Give it a try.
If you have variations that work for you, do share with me as a reply.