It definitely is an interesting idea @chbartist to divide a day into smaller portions - my individual "days". It sounds good in theory, but with a 9-5 job and the time it takes me to get ready in the morning and to go to the office and back home again, 12 hours of the "official" day are already gone.

My day is automatically diveded into two portions - the "work for my boss" day and the "I do my stuff" day.

I usually get about 5 hours of sleep. But: I lose time during my "I do my stuff" day, because I simply fall asleep in front of my screen because I am just too tired.

So as I said, your ideas is an interesting concept, but I doubt that it is a realistic option for everybody.