I think it comes from “both ends of the day” meaning you need candle light before sunrise and after sunset because you’re working for so many hours :). You could also say “I’ve been worked off my feet” or “I’m snowed under with work” to mean you’re basically working very hard 24/7 😀

It basically means you are trying to cram too much into your life.

Burning the candle at both ends means you stay up late - often partying, then get up early - there's not enough sleep and you're living hard!

It means you get up early and go hto bed very late.