Oh yeah man I'm totally with you on that. My unproductive side takes over on those days: "Hmm could work on that project... na feeling a bit sleepy, how about some video games... just a bit..."
I'm the opposite. When I'm sleep deprived menial tasks don't seem as boring as they do normally, since I need my full attention to do them with the limited brain capacity.
Throw in spending three 8+ hour days working on an inception deck. Then do a 2 hour sprint planning meeting, spend 1.5 days working, then a 2 hour sprint review meeting.
Then throw in a pivot every 2 or 3 weeks, involving a new inception deck.
Why were they that long? There could be many valid reasons to have a sprint planning that takes 4 hours. If 4 hours every 2 weeks is the only planning type meeting you have that is pretty good.
So much of "Agile"/Scrum, at least in practice, is passive-aggressive, collective punishment. The team is judged to be underperforming, thus subjected to painful, useless meetings and degrading process that might turn zeros into just-barely-employable 0.5x programmers but bring the 10x down to zombie levels.