We can never judge the lives of others, because each person knows only their own pain and renunciation. It's one thing to feel that you are on the right path, but it's another to think that yours is the only path.
No fairer destiny could be allotted to any physical theory than that it should of itself point out the way to the introduction of a more comprehensive theory, in which it lives on as a limiting case.
Keep away from people who try to belittle your ambitions. Small people always do that, but the really great make you feel that you, too, can become great.
It sometimes strikes me how immensely fortunate I am that each day should take its place in my life, either reddened with the rising and setting sun, or refreshingly cool with deep, dark clouds, or blooming like a white flower in the moonlight. What untold wealth!