I tracked my own "focus decay" for two weeks, turns out my best hour isn't when I thought it was

Ran a small experiment on myself: for two weeks, every time I noticed my focus slipping (checking phone, re-reading the same line, opening a new tab for no reason), I logged the time. No app, just a notes file.

Expected the drop-off to happen after lunch. It didn't. My focus was sharpest almost exactly 90 minutes after I started working, then fell off a cliff, way earlier than the classic "afternoon slump" advice everyone repeats. Mornings weren't actually my peak, minute 90 of deep work was.

Made me question how much of the standard productivity advice (morning person vs night owl, post-lunch dip, etc.) is actually generic and not personal at all.

If you've ever tracked your own focus patterns instead of assuming the general advice applies to you, what did you actually find? Anyone else's "peak hour" turn out to be somewhere unexpected?