Pleasure in itself harmless may become mischievous by endearing to us a state which we know to be transient and probatory, and withdrawing our thoughts from that of which every hour brings us nearer to the beginning, and of which no length of time will bring us to the end.
 Samuel Johnson, The History of Rasselas, Prince of Abissinia (1759). copy citation

Context

““ The liberty of using harmless pleasures, ” proceeded Imlac, “ will not be disputed, but it is still to be examined what pleasures are harmless. The evil of any pleasure that Nekayah can image is not in the act itself but in its consequences. Pleasure in itself harmless may become mischievous by endearing to us a state which we know to be transient and probatory, and withdrawing our thoughts from that of which every hour brings us nearer to the beginning, and of which no length of time will bring us to the end. Mortification is not virtuous in itself, nor has any other use but that it disengages us from the allurements of sense. In the state of future perfection to which we all aspire there will be pleasure without danger and security without restraint. ”
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