"On the Shortness of Life," by Seneca the Younger... written over a thousand years ago, yet a timeless reminder to live in the moment.
"Why do you torment yourself and lose weight over some problem....
I have no time for such nonsense; a mighty undertaking is on my hands. What am I to do? Death is on my trail, and life is fleeting away; teach me something with which to face these troubles. Bring it to pass that I shall cease trying to escape from death, and that life may cease to escape from me. Give me courage to meet hardships; make me calm in the face of the unavoidable. Relax the straitened limits of the time which is allotted me. Show me that the good in life does not depend upon life's length, but upon the use we make of it; also, that it is possible, or rather usual, for a man who has lived long to have lived too little. Say to me when I lie down to sleep: 'You may not wake again!' And when I have waked: 'You may not go to sleep again!' Say to me when I go forth from my house: 'You may not return' And when I return: 'You may never go forth again!' You are mistaken if you think that only on an ocean voyage there is a very slight space between life and death. No, the distance between is just as narrow everywhere. It is not everywhere that death shows himself so near at hand; yet everywhere he is as near at hand.
Rid me of these shadowy terrors; then you will more easily deliver to me the instruction for which I have prepared myself. At our birth nature made us teachable, and gave us reason, not perfect, but capable of being perfected. Discuss for me justice, duty, thrift, and that twofold purity, both the purity which abstains from another's person, and that which takes care of one's own self. If you will only refuse to lead me along by-paths, I shall more easily reach the goal at which I am aiming. For, as the tragic poet says:
The language of truth is simple.
We should not, therefore, make that language intricate; since there is nothing less fitting for a soul of great endeavour than such crafty cleverness. Farewell."