There’s nothing quite like starting (or ending) your day with a cold shower.
It’s great for your immune system and, for me, I found completing a cold shower gave me more energy for the day and a sense that I’d already accomplished something difficult.
Suggested habit: “Cold shower” or “End shower on cold”
You can “warm up” to a cold shower by ending each shower on cold (target 15-30 seconds). Or just jump to it. It’s much easier if you take a cold shower right after some deep breathing.