How do you know when to stop tweaking study?

I know this is a tiny sample size, but after 8 attempts the pattern is pretty clear. When I keep the setup simple, I actually follow through.

I had a disappointing first try, a surprisingly good second try, and then a third attempt that taught me humility. So, naturally, I now have opinions.

Would love to hear how other people handle this. I am especially curious about the version that works on a tired weekday, not just on an ideal Sunday.