Comment by Eddy_Viscosity2

I likewise have about 4 good hours of thinking work capacity in a day. But even finding that can difficult because you have to navigate all the trivial non-thinking admin tasks, meetings, forms, approvals, and other soul-sucking semi-work which does not progress a project, but yet a project can exist without. Management will always find a way to fill up every last minute with this category of non-thinking semi-work so its a fight to even find a little window to do the hard thinking work.