"The time will come when diligent research over long periods will bring to light things which now lie hidden. A single lifetime, even though entirely devoted to the sky, would not be enough for the investigation of so vast a subject... And so this knowledge will be unfolded only through long successive ages. There will come a time when our descendants will be amazed that we did not know things that are so plain to them... Many discoveries are reserved for ages still to come, when memory of us will have been effaced." ― Seneca, Natural Questions
For what prevents us from saying that the happy life is to have a mind that is free, lofty, fearless and steadfast - a mind that is placed beyond the reach of fear, beyond the reach of desire, that counts virtue the only good, baseness the only evil, and all else but a worthless mass of things, which come and go without increasing or diminishing the highest good, and neither subtract any part from the happy life nor add any part to it?
A man thus grounded must, whether he wills or not, necessarily be attended by constant cheerfulness and a joy that is deep and issues from deep within, since he finds delight in his own resources, and desires no joys greater than his inner joys." - Seneca, The Stoic Philosophy of Seneca: Essays and Letters (De Providentia, De Brevitate Vitæ, De Tranquillitate Animi, Ad Helviam matrem De consolatione, De Clementia, Epistulae morales ad Lucilium
"We might never rid ourselves of a lingering anxiety regarding our death; this is a kind of tax we pay in return for self-awareness." - Derren Brown, Happy: Why More or Less Everything is Absolutely
"At dawn, when you have trouble getting out of bed, tell yourself, "I have to go to work - as a human being. What do I have to complain of, if I'm going to do what I was born for - the things I was brought into the world to do? Or is this what I was created for? To huddle under the blankets and stay warm?" - Marcus Aurelius, Meditations
"In conformity with this spirit and aim of the Stoa, Epictetus begins with it and constantly returns to it as the kernel of his philosophy, that we should bear in mind and distinguish what depends on us and what does not, and thus should not count on the latter at all. In this way we shall certainly remain free from all pain, suffering, and anxiety. Now what depends on us is the will alone, and here there gradually takes place a transition to a doctrine of virtue, since it is noticed that, as the external world that is independent of us determines good and bad fortune, so inner satisfaction or dissatisfaction with ourselves proceeds from the will. But later it was asked whether we should attribute the names *bonum et malum* to the two former or to the two latter. This was really arbitrary and a matter of choice, and made no difference. But yet the Stoics argued incessantly about this with the Peripatetics and Epicureans, and amused themselves with the inadmissible comparison of two wholly incommensurable quantities and with the contrary and paradoxical judgements arising therefrom, which they cast on one another. An interesting collection of these is afforded us from the Stoic side by the *Paradoxa* of Cicero." - from-The World as Will and Representation_. Translated from the German by E. F. J. Paye in two volumes: volume I, pp. 88-89" ― Arthur Schopenhauer
"Hang on to your youthful enthusiasms -- you'll be able to use them better when you're older." ― Seneca