Do you keep a gig diary, or is that overkill when you're new?

I’m starting to lose track of what I actually changed between gigs. I can remember whether the night felt good or bad, but not always which version of a bit I used or what I meant to test next. Do people keep a basic gig diary from the start — date, set, what worked, one thing to change — or does that become admin you never look at again?