There’s a reason why the military has boot camps, why Olympic gymnasts treat each practice as if it were an international competition, why Seth Godin’s famous alt-MBA demands 30+ hours of work per week and 13 completed projects in a month, all for students who have full-time jobs.

Part of the reason is the training itself. Army recruits come together when they’ve gone through a harrowing experience together. Gymnasts get stronger and more fit when they work that hard. And you learn loads by knocking out project after project such a short period of time.

But the real impact is on the psychology of each participant: the act of discovering how much you can accomplish—how much more than you thought you could—resets your internal bar. Whether it’s your psychological threshold for pain, the amount of heat or number of pushups you can withstand before you start to panic, or simply a new perspective what you can produce when you sprint, the most valuable part of these sorts of experience is to expand your sense of what is possible.

Pushing through gives you that unique ability captures so effortlessly by Nigel Tufnel, the fictional lead guitarist in Spinal Tap: when you need that little bit of extra juice, it makes all the difference to have an amp that goes up to 11.