What we learn from history is that people don't learn from history.

If you're not stubborn, you'll give up on experiments too soon. And if you're not flexible, you'll pound your head against the wall and you won't see a different solution to a problem you're trying to solve.

Deep into that darkness peering, long I stood there wondering, fearing, doubting, dreaming dreams no mortal ever dared to dream before.

A good world needs knowledge， kindliness， and courage； it does not need a regretful hankering after the past or a fettering of the free intelligence by the words uttered long ago by ignorant men.