The question I see come up most here: why does crashing after a good day feel crueler than a regular bad one? Eighteen months in, I have some partial answers. The good day usually isn’t a sign things are turning. It’s more often a sign you drew down reserves you didn’t know you had.
By the time you feel well enough to cook dinner or follow a conversation, you’ve already exceeded your anaerobic threshold. The crash isn’t caused by the good day - it’s the receipt for it, arriving 36-48 hours later. A few things I’ve found genuinely useful to understand: The delay is physiological, not psychological. You can feel completely fine in the moment and still be borrowing against tomorrow.
Resting HR often climbs before the crash arrives. I added a continuous HR monitor around month 14 and found mine rises 8-12 BPM in the day or two before a full crash hits. That changed how I pace, or try to. The pattern is easier to spot in retrospect than it is live.
I note fatigue level throughout the day from my watch face - enough friction removed that I actually do it consistently, which is the only reason I have data at all. The hardest part isn’t understanding PEM intellectually. It’s trusting the warning when you feel fine. Has anyone found a reliable early signal that consistently predicts a crash before it fully arrives?