"We are what we repeatedly do. Excellence, then, is not an act, but a habit."

The artist must be a witness to the invisible.

El hombre más poderoso es el que es dueño de sí mismo.

You are too generous to trifle with me. If your feelings are still what they were last April, tell me so at once. My affections and wishes are unchanged, but one word from you will silence me on this subject forever.

In the realm of theoretical physics, every discovery opens up new questions and challenges.

You have to believe in yourself when no one else does.