Why is it that during specific hours/time of the day, I feel more focused and wanting to grind LC?

I notice that my brain wants to grind LC and study after 11PM and for the time before that, my brain would wander everywhere if I tried to study LC.

I'm using this to my advantage to study as many as 2-3 questions a night but I only have a limited amount of time before I have to go to bed. I wish my brain was wired to study without it being 11PM.