The Wim Hof Method

Don't push past all your perceived limits, right? That's where they don't always go out for the most extreme thing. Realize that there are limits and you have to pull back way before then. And of course, don't hyperventilate in water ever. If you see someone hyperventilating water, tell them it's a really bad idea because that's how people drown. Even if you've done it once or twice successfully, it doesn't mean you'll do it successfully all the time.