"A profound unmitigated loneliness is the only truth of life"
- R.K. Narayan

Context: A man and woman cross each others' path

Case 1: Both in depressed state of mind.
Result: Only a depressed person can truly understand another. They share their pains and connect instantly. Through the channel of sadness, they fall in love.

Case 2: One depressed, other happy (i.e. not depressed).
Result: The (relatively) happier one truly feels great sympathy for the depressed one. The happier one knows the value of happiness and understands that the other is missing it. Through the channel of empathy, they fall in love.

Case 3: Both in happy state of mind.
Result: They sing, dance and truly share goodness. The talk beautiful things; and see a glow in each others' happiness. They understand that they could give more happiness to each other. Through the channel of joy, they fall in love.