saudade (european portuguese : [sɐwˈðaðɨ])

​- a deep emotional state of nostalgic or profound melancholic longing for an absent something or someone that one loves and often carries a repressed knowledge that the object of longing might never return.

“the feelings that hurt most, the emotions that sting most, are those that are absurd - the longing for impossible things, precisely because they are impossible; nostalgia for what never was; the desire for what could have been; regret over not being someone else; dissatisfaction with the world’s existence. all these half-tones of the soul’s consciousness create in us a painful landscape, an eternal sunset of what we are.” 
― fernando pessoa