“Why didn't I learn to treat everything like it was the last time. My greatest regret was how much I believed in the future.”

Source: Extremely Loud and Incredibly Close

The Stranger (1942)

Deeds Rather Than Words (1963)
Context: I don't believe in playing down to children, either in life or in motion pictures. I didn't treat my own youngsters like fragile flowers, and I think no parent should.
Children are people, and they should have to reach to learn about things, to understand things, just as adults have to reach if they want to grow in mental stature. Life is composed of lights and shadows, and we would be untruthful, insincere, and saccharine if we tried to pretend there were no shadows. Most things are good, and they are the strongest things; but there are evil things too, and you are not doing a child a favor by trying to shield him from reality. The important thing is to teach a child that good can always triumph over evil, and that is what our pictures attempt to do.

Thoughts on Man's Purpose in Life (1974), Exchange with Admiral Rickover (1982)
Context: I do not have regrets. I believe I helped preserve the peace for this country. Why should I regret that? What I accomplished was approved by Congress — which represents our people. All of you live in safety from domestic enemies because of security from the police. Likewise, you live in safety from foreign enemies because our military keeps them from attacking us. Nuclear technology was already under development in other countries. My assigned responsibility was to develop our nuclear navy. I managed to accomplish this.

Source: Running with Scissors

1970s, BOBBY FISCHER SPEAKS OUT! (1977)

Source: Extremely Loud and Incredibly Close

Speech, New York City (12 December 1964).
Attributed

Source: Diane Sawyer interview (ABC, 1993)