怎样能让你身心都更强大？

What helps you grow stronger physically, emotionally, mentally or even spiritually?
什么有助于使你在身体上、感情上、头脑上甚至精神上更强大？

获得11.2k好评的回答@Darren Beattie：

In one word?
用一个字总结？
Stress
压力
Then consequent adaptation.
然后就适应了。
People have this firm belief that all 'stress' = Bad. But stress is merely a force acting upon you. Otherwise known as a stimulus. This could be expressed as 'being outside of your comfort zone' or dealing with 'change.'
人们坚信所有的“压力”都不好。但压力只是作用在你身上的一种力量，还可以叫“刺激”，可以表述为“离开舒适区”或应对“改变”。
However, an easy argument for the proliferation of the human race exists that human beings are among the most adaptable organisms on the planet. Our creativity and ingenuity has allowed us to thrive on every continent in nearly any environment, even really harsh ones like the Arctic Circle, Antarctica, The Plains of Africa, The Outback, The Sohara and dense jungles like the Amazon.
然而人类生存繁衍生息的一个很容易理解的原因就是人类是地球上适应能力最强的物种之一。我们的创造力和足智多谋使我们能在所有陆地上几乎任何环境下都能繁衍，甚至是条件极其恶劣的地区，如北极圈、南极、非洲平原、澳大利亚内地、撒哈拉沙漠和亚马逊这样的密林。
Ultimately it's adaptation to stress that determines how we advance as people, the same way a plant generally grows towards the stress of sunshine, or adapts to the chemical makeup of the soil it's in, or responds to rain.
基本上是对压力的适应决定了我们作为人类如何发展，和植物逐渐向光生长、适应土壤中化学物质或应对雨水是一个道理。
The key here is that if the stress is too high, we adapt poorly；if the stress is too low, we don't adapt at all. The stress needs to be just right and it needs to be applied deliberately over a period of time to yield an adaptation.
这里的关键是如果压力太大，我们就不容易适应；如果压力太小，我们就无需适应。压力需要恰到好处，而且要刻意持续一段时间才能最终让人适应。
Often one dose of stress is not enough to force continued adaptation either. So continued development requires steady progression as well.
通常一次压力不够引起持续适应，所以持续的发展需要有持续的压力。
For instance. If you want to get good at math, you need to practice math problems that are continually challenging enough to make you really think about the answer. Once you understand the underlying concepts to the answer of 3+3 to a point of automaticity, you have to eventually practice more complex problems like 5 + 3, or 3 + 3 + 3. If you don't slightly over-reach on ability constantly, you get stagnant progress and thus 'do not grow stronger.
比如，如果你想数学学得好，需要一直做有难度的数学题才能使你真正去思考答案。一旦你深入理解了3+3的答案并达到脱口而出的程度，你要继续练习更复杂的题如5+3或3+3+3，如果你不持续少量增加难度，就会停滞不前，也就不能变得“更强”。
Bottomline: You can't have adaptation without an appropriate stimulus.
总结：没有适当的刺激，你就不能适应。