A passage from Chrysippus
Chrysippus, Fragments (in Plutarch, On Stoic Self-Contradictions) 1042D
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When a man fixes his hope upon what is to come, considering that what is present is sufficient and welcome, he gains the most.
Related passages
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Men seek retreats for themselves, houses in the country, sea-shores, and mountains... But this is altogether a mark of the most common sort of men, for it is in thy power whenever thou shalt choose to retire into thyself.
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At dawn, when you have trouble getting out of bed, tell yourself: 'I have to go to work — as a human being.'
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Your present opinion founded on understanding, your present conduct directed to social good, your present disposition contented with everything that happens — that is enough.