Think of happiness as the sun, and sadness as rain. The sun can fill you with warmth and energy, making the road ahead bright and enjoyable. Rain, however, usually hinders, making it difficult to see what lies ahead. Despite this, if the sun shines too brightly, it can scorch and burn, accidentally hurting those who bask in it's shine. That's where the rain is needed. It can cool the burning heat that would otherwise burn everything. All things need rain, for one reason or another. We too, as humans, depend on the rain, regardless if it appears to hinder us, if we are to survive to our fullest extent.