Even if all the bright intellects who ever lived were to agree to ponder this one theme, they would never sufficiently express their surprise at this fog in the human mind. Men do not let anyone seize their estates, and if there is the slightest dispute about their boundaries they rush to stones and arms; but they allow others to encroach on their lives--why, they themselves even invite in those who will take over their lives. You will find no one willing to share out his money; but to how many does each of us divide up his life! people are frugal in guarding their personal property; but as soon as it comes to squandering time they are most wasteful of the one thing in which it is right to be stingy. So, I would like to fasten on someone from the older generation and say to him; "I see that you have come to the last stage of human life; you are close upon your hundredth year, or even beyond: come now, hold an audit of your life. Reckon how much of your time has been taken up by a money-lender, how much by a mistress, a patron, a client, quarreling with your wife, punishing your slaves, dashing about the city on your social obligations. Consider also the diseases which we have brought on ourselves, and the time too which has been unused. You will find that you have fewer years than you reckon. Call to mind when you ever had a fixed purpose: how few days have passed as you planned; when you were ever at your own disposal; when your face wore it's natural expression; when you mind was undisturbed; what work have you achieved in such a long life; how many have plundered your life when you were unaware of your losses; how much you have lost through groundless sorrow, foolish joy, greedy desire, the seductions of society; how little of your own was left to you. You will realize that you are dying prematurely.
So what is the reason for this? You are living as if destined to live forever; your own frailty never occurs to you; you don't notice how much time has already passed, but squander it as though you had a full and overflowing supply--though all the while that very day which you are devoting to somebody or something may be your last. You act like mortals in all that you fear, and like immortals in all the you desire. You will hear many people saying: "When I am fifty I shall retire into Leisure; when i am sixty I shall give up public duties." And what guarantee do you have of a longer life? Who will allow your course to proceed as you arrange it? Aren't you ashamed to keep for yourself just the remnants of your life and to devote to wisdom only the time which cannot be spent on any business? How late it is to begin really to live just when life must end? How stupid to forget our mortality, and put off sensible plans to our fiftieth and sixtieth years, aiming to begin life from a point at which few have arrived.
from seneca's On the Shortness of Life - life is long if you know how to use it
highlighted passages represent my notes