From Marcus Aurelius’ Meditations

Book 2.6

Wrong, wrong thou art doing to thyself, O my soul; and all too soon thou shalt have no more time to do thyself right. Man has but one life; already thine is nearing its close, yet still hast thou no eye to thine own honour, but art staking thy happiness on the souls of other men.

The art of living in the moment-being the best one can be in any one moment, as that will lead to always being one’s best-is brought up by wise men of all stripes, but you really see it in Stoicism, Existentialism and Buddhism, some of my favourite subjects. What would the world be like if at every moment people consciously chose to emulate their ideal human.