You can't force crops from rich soil forever. If you plant heavy crops without a break, you'll exhaust the land's fertility. The same thing happens to our minds. Constant work destroys their liveliness. But they recover their strength after a short rest. Non-stop effort creates a kind of numbness and sluggishness. People wouldn't crave play and fun so much if these things weren't naturally appealing. But constant indulgence in them destroys all seriousness and strength of mind. Sleep is also necessary for refreshment. But if you sleep for days and nights straight, it becomes death. There's a big difference between loosening your grip on something and letting it go entirely.
We must not force crops from rich fields, for an unbroken course of heavy crops will soon exhaust their fertility, and so also the liveliness of our minds will be destroyed by unceasing labour, but they will recover their strength after a short period of rest and relief: for continuous toil produces a sort of numbness and sluggishness. Men would not be so eager for this, if play and amusement did not possess natural attractions for them, although constant indulgence in them takes away all gravity and all strength from the mind: for sleep, also, is necessary for our refreshment, yet if you prolong it for days and nights together it will become death. There is a great difference between slackening your hold of a thing and letting it go.