Juggling glass balls and rubber balls

This version is not as good as Phil's but is attributable to Brian G. Dyson and does a decent enough job of it:

"Imagine life as a game in which you are juggling some five balls in the air. You name them - work, family, health, friends and spirit - and you're keeping all of these in the air. You will soon understand that work is a rubber ball. If you drop it, it will bounce back. But the other four balls - family, health, friends and spirit - are made of glass. If you drop one of these, they will be irrevocably scuffed, marked, nicked, damaged or even shattered. They will never be the same. You must understand that and strive for balance in your life."