It means too much working and not enough enjoyment leads to inefficiency, and may make you bored or boring. The sentiment expressed here was first recorded by the Egyptian sage Ptah-Hotep in 2400 B.C. The more familiar modern saying appeared first in 1659, and was included in later collections of proverbs.

Übersetzung:

immer nur arbeiten macht nicht glücklich

Gegenteil(e)

The opposite of "all work and no play (makes Jack a dull boy)" is "to have a wide range of interests".

Synonym(e):

You could also say: too much working and not enough enjoyment leads to boredom.