all work and no play makes Jack a dull boy

All work and no play makes Jack a dull boy (working too hard and not taking the time to have fun is bad for you.) ≅ От работы и кони дохнут; ≅ работа не волк — в лес не убежит

Common Usage: This is a very well known proverb, often used as an excuse to go out and party, or to convince a hard worker to come out and party.

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Literal Origins: Too little time set aside for games and fun can make young boys stupid. It was originally used as a warning to parents about working their children too hard.