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.
It's only those exceptional and rare individuals who have brilliant ideas delivered to them by the muse, complete and gift wrapped. The rest of us have to work at it.