“So we had enough for one more day.--And it is by the day I live. Were I to think of how it will be a year or even a month hence, I should be tried indeed—yea, greatly tried. "Sufficient unto the day is the evil thereof," is my Lord's own precious warrant for this. He will not have me to be anxious about tomorrow, and therefore I cast my cares about tomorrow upon Him.”

Remarks at a farewell dinner address in New York (20 May 1905), later published in Aequanimitas, and Other Addresses (1910 edition), p. 473.
Context: I have had three personal ideals: One to do the day's work well and not to bother about tomorrow. You may say that is not a satisfactory ideal. It is; and there is not one which the student can carry with him into practice with greater effect. To it more than anything else I owe whatever success I have had — to this power of settling down to the day's work and trying to do it well to the best of my ability, and letting the future take care of itself.
The second ideal has been to act the Golden Rule, as far as in me lay, toward my professional brethren and toward the patients committed to my care.
And the third has been to cultivate such a measure of equanimity as would enable me to bear success with humility, the affection of my friends without pride, and to be ready when the day of sorrow and grief came, to meet it with the courage befitting a man.
What the future has in store for me, I cannot tell — you cannot tell. Nor do I care much, so long as I carry with me, as I shall, the memory of the past you have given me. Nothing can take that away.

Barry Edward O'Meara, in Napoleon in Exile : or, A Voice from St. Helena (1822), Vol. II, p. 155
About
Context: "What do you think," said he, "of all things in the world would give me the greatest pleasure?" I was on the point of replying, removal from St. Helena, when he said, "To be able to go about incognito in London and other parts of England, to the restaurateurs, with a friend, to dine in public at the expense of half a guinea or a guinea, and listen to the conversation of the company; to go through them all, changing almost daily, and in this manner, with my own ears, to hear the people express their sentiments, in their unguarded moments, freely and without restraint; to hear their real opinion of myself, and of the surprising occurrences of the last twenty years." I observed, that he would hear much evil and much good of himself. "Oh, as to the evil," replied he, "I care not about that. I am well used to it. Besides, I know that the public opinion will be changed. The nation will be just as much disgusted at the libels published against me, as they formerly were greedy in reading and believing them. This," added he, "and the education of my son, would form my greatest pleasure. It was my intention to have done this, had I reached America. The happiest days of my life were from sixteen to twenty, during the semestres, when I used to go about, as I have told you I should wish to do, from one restaurateur to another, living moderately, and having a lodging for which I paid three louis a month. They were the happiest days of my life. I was always so much occupied, that I may say I never was truly happy upon the throne."

Source: Someone Like You

Source: Journey to the End of the Night (1932), Chapter 4

If Tomorrow Never Comes, written by G. Brooks and Kent Blazy.
Song lyrics, Garth Brooks (1989)

The Cherubinic Wanderer

Source: Extremely Loud and Incredibly Close

Source: Gone with the Wind