Own the Day, Own Your Life: Optimized Practices for Waking, Working, Learning, Eating, Training, Playing, Sleeping, and Sex

by Aubrey Marcus

But it is not until the method is paired with cold exposure that it becomes truly life altering—a mechanism for both healing and growth. That is because without the cold there is no external resistance to tell you when enough is enough. There is no force outside the physical capacity of your lungs to push against to guide your sense of progress. There is no acute stress. This is not a revolutionary concept. We have known for millennia that resistance is the shortest path to growth. “As iron sharpens iron, so one person sharpens another,” says the Old Testament (Proverbs 27:17). Put more weight on the bar, you get stronger. Run harder, you get faster. It’s a form of good, acute stress known as hormesis.