A Thousand Paper Cranes. Peace on Earth and in the Heavens.
Inscribed, in the handwriting of Yukawa, on the surface of the bell inside the Children's Peace Monument at Hiroshima, Japan. The crane is a symbol of longevity and happiness in Japan. The monument to mourn all the children whose death was caused by the atomic bomb was inspired by 12-year-old Sadako Sasaki, who believed that if she could fold 1000 paper cranes she would be cured of the leukemia that resulted from her exposure to the radiation of the atomic bomb when two years old. She died before completing them.

I do not want to write beyond this point, because those days when I studied relentlessly are nostalgic to me; and on the other hand, I am sad when I think how I have become increasingly preoccupied with matters other than study.
Explaining in his autobiography why he went no further in recording his life therein than 1934, when he published his paper describing his great discovery.

Nature creates curved lines while humans create straight lines.

Reality is complicated. There is no justification for all of the hasty conclusions.

Reality is cruel. All of the naivete is going to be removed. Reality is always changing, and it is always unpredictable. All of the balance is going to be destroyed.

Suppose there is something which a person cannot understand. He happens to notice the similarity of this something to some other thing which he understands quite well. By comparing them he may come to understand the thing which he could not understand up to that moment. If his understanding turns out to be appropriate and nobody else has ever come to such an understanding, he can claim that his thinking was really creative.