此生幸福的三大要素是:有事可做,有爱可依,有希望可期。
Three grand essentials to happiness in this life are something to do, something to love, and something to hope for.
解释:既要追悔以往的过失,也要预防将来可能发生的错误。
数学的美在于它能够以最抽象的术语描述宇宙。