The grand question tends to sit unanswered. "What do I want from my life" is true and important and almost impossible to pick up on a Tuesday evening. It asks for more than the moment has to give, so the moment gives nothing.
A smaller question is easier to hold. "What felt heavy today, and why" fits inside the time you actually have. It does not ask you to solve anything, only to notice. And noticing, kept up over weeks, tends to gather into something the grand question could not reach directly.
There is no prize for the hardest prompt. The one worth keeping is the one you will still answer honestly when you are tired. Often that is the plainest one on the page.