Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones.
Because men really respect only that which was founded of old and has developed slowly, he who wants to live on after his death must take care not only of his posterity but even more of his past.
When the Special Theory of Relativity began to germinate in me, I was visited by all sorts of nervous conflicts... I used to go away for weeks in a state of confusion.
And indeed there will be time To wonder, "Do I dare?" and, "Do I dare?" Time to turn back and descend the stair, With a bald spot in the middle of my hair.