说出口的话无法收回，听到的话无法忘记。

Your smarts will come in handy because you will travel in a land of marvels. We humans -- plodding as we are -- will astonish ourselves. We'll invent ways to generate clean energy and a lot of it. Atom by atom， we'll assemble tiny machines that will enter cell walls and make repairs. This month comes the extraordinary but also inevitable news that we've synthesized life. In the coming years， we'll not only synthesize it， but we'll engineer it to specifications. I believe you'll even see us understand the human brain. Jules Verne， Mark Twain， Galileo， Newton -- all the curious from the ages would have wanted to be alive most of all right now. As a civilization， we will have so many gifts， just as you as individuals have so many individual gifts as you sit before me.

今天很残酷，明天更残酷，后天很美好，但绝对大部分是死在明天晚上，所以每个人不要放弃今天。