Simon

“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.”
― Seneca, On the Shortness of Life

“The greatest obstacle to living is expectancy, which hangs upon tomorrow and loses today. You are arranging what lies in Fortune’s control, and abandoning what lies in yours. What are you looking at? To what goal are you straining? The whole future lies in uncertainty: live immediately.”
― Seneca, On the Shortness of Life

“You become what you give your attention to.”
― Epictetus, The Art of Living: The Classical Manual on Virtue, Happiness and Effectiveness

“It is not that we have a short time to live, but that we waste a lot of it. Life is long enough, and a sufficiently generous amount has been given to us for the highest achievements if it were all well invested. But when it is wasted in heedless luxury and spent on no good activity, we are forced at last by death’s final constraint to realize that it has passed away before we knew it was passing. So it is: we are not given a short life but we make it short, and we are not ill-supplied but wasteful of it… Life is long if you know how to use it.”
― Seneca, On the Shortness of Life: Life Is Long if You Know How to Use It