Alertness follows a curve set by your body clock. For most men it peaks late morning, dips after lunch, and comes back mid-afternoon. Night people run the whole curve later.
Doing difficult work in your trough takes longer and comes out worse. Same work in your peak feels easy. Evidence: decent
Two days of noting when you feel sharp is enough to find your hours.
Same theme: Through the day
Through the day
Move for the tiredness
Too tired to train? Go anyway, and go easy, at a pace you could talk at. Three times a week for six weeks, then judge.
3x a weekEvidence: decent
Through the day
Stairs before the coffee
Afternoon slump? Walk up and down the stairs for ten minutes before you buy the coffee. Then decide if you still want it.
10 minEvidence: worth trying
Through the day
Swap the task, don't push through
When the hard thinking stops moving late in the day, switch to easy work. Big decisions wait until you're fresh.
no timeEvidence: worth trying