From CNBC:
Twitter and Square CEO Jack Dorsey (42) walks 5 miles to work every day, eats just 1 meal a day, fasts all weekend, and tries to meditate two hours a day. CNBC looked at 11 of his”wellness” customs, which he spoke on a recent episode of the Ben Greenfield Fitness podcast.

“Nothing has given me more mental confidence than Having the Ability to go straight from room temperature to the chilly,” Dorsey says.” [E]specially in the morning, going in an ice-cold tub from just being warm in bed is — it just unlocks this thing in my head and I feel as if I can will myself to do this thing that seems so modest but hurts so much, I could do nearly anything.”