There's exactly one number that matters at 6:40 a.m., and it isn't your inbox. It's your HRV — and it changes the whole day.

Read it before the coffee

Caffeine raises your heart rate and shifts the gap between beats. Read your HRV in the first two minutes after waking, before the kettle, and you get a clean baseline. After coffee, the number is already lying.

It's a range, not a grade

A single HRV number means nothing. Your 30-day range means everything. Above your baseline — recovered. Below it — back off. That's the whole read.