如果没有过去充当我们的参照系，我们就会浑然不知我们将去向何方。

Without the past serving as a framework of reference, we would not know where we are heading for.

youdao

如果没有你，没有过去，我不会有伤心。

If have no you, not the past, I will not have a sad.

youdao

如果你过去一直是快乐的感受情绪能引出你以前没有过的想法。

Feeling emotional can bring out ideas you would have never had if you were always happy.

youdao

So you should have gotten two handouts as you came in, and if you didn't, please raise your hand and a TA will come to you and get you that second handout.

因此你们应该都在进来的时候拿到了两份讲义，如果你没有，请举手示意，助教会过去,给你第二份讲义。

麻省理工公开课 - 化学原理课程节选