Balance.

Cartier Bresson, Armenia, USSR, 1972

Sadness gives depth. 
Happiness gives height. 
Sadness gives roots. 
Happiness gives branches. 
Happiness is like a tree going into the sky, and sadness is like the roots going down into the womb of the earth. 
Both are needed, and the higher a tree goes, the deeper it goes, simultaneously. 
The bigger the tree, the bigger will be its roots. In fact, it is always in proportion. 
That's its balance.

Osho