Saudade is a emotion you likely didn’t know you didn’t have a word for. At heart, it is an extension of the ‘homesick’ concept beyond a location to people you’ve known or things from your past. You’re allowed to apply that sort of yearning for more than just the place of your childhood. It’s the presence of an absence, one of many feelings for absence.
The word is Portuguese and it contains complexities beyond homesick. The canonical example is the sailor or soldier who has left you and the feeling you’re left with without them. You’re happy that you knew them and you’re unsure whether they’ll live to return but you remain hopeful (against your better judgment).
Contrast nostalgia. The target of nostalgia is strictly confined to the past. Saudade is a turning away from the present, toward either the past or future. The Portuguese have the word ‘nostalgia’. Nostos Algos; returning-home pain. What the soldier away from home feels, not what the dual emotion that the family feels for the soldier.
One of the additional complexities is that you can feel saudade yearning toward a thing that never existed. All it requires is the obsession. Probably some intersection with golden age thinking.
If you haven’t felt this emotion, isn’t that interesting? Did you not feel it because you didn’t have the word and, having never meet the concept, weren’t prepared for it?
Of a similar vein is the German concept sehnsucht, a portmanteau for yearning/addiction. The thing you seek is not possible, the traces of it only shadows. Addiction is easy in a sense. No choice is required not to quit, no agency necessary. It’s a clean decision, simply continue with your addiction. You can even convince yourself that being a non-renouncer is noble. Compare with Kierkegaard’s whimsically named knight of infinite resignation.