Day 1: I lasted 45 seconds in a cold shower and thought I was dying.
Day 400: I sit in 39°F water for 5 minutes and it feels like coming home.
Here's what actually changed — backed by my own data and subjective experience, not broscience.
What improved measurably: - Morning cortisol response: faster wake-up, more consistent energy - HRV: up 18% average over 12 months (measured via Whoop) - Skin: noticeably clearer, less inflammation - Recovery: post-workout soreness cut roughly in half