Burn the candle at both ends
To live at a hectic pace.
Our current understanding of this phrase is of a life lived frenetically and unsustainably - working or enjoying oneself late into the night only to begin again early the next day. It didn't having that meaning when it was first coined in the 18th century.
Don't try this at home.
The 'both ends' then weren't the ends of the day but were a literal reference to the two ends of a candle. Candles were useful and valuable (see not worth the candle) and the notion of waste suggested by lighting both ends at once implied reckless waste. This thought may well have been accentuated by the fact that candles may only be lit at both ends when held horizontally, which would cause them to drip and burn out quickly.
Nathan Bailey defined the term in his Dictionarium Britannicum, 1730, by which time the phrase had already been given a figurative interpretation and the 'both ends' were a husband and wife:
"The Candle burns at both Ends. Said when Husband and Wife are both Spendthrifts."
Like not worth the candle, the phrase derives from an earlier French version. Randle Cotgrave recorded it in A Dictionarie of the French and English Tongues, 1611:
'Brusler la chandelle par les deux bouts'. [To burn the candle by the two ends]
See also, hold a candle.