There's a Japanese word that encapsulates a rather permeating and sticky feeling of pain and difficulty perfectly; 辛い. And the part that makes you go, "Ah, yes. That is the word that describes my feelings." is when you can combine 辛い with another word to make that succinct compound.

You are 思い辛い. Ever since that day, whenever you are thought of, it is 辛い. Sometimes I am tinged with it, other times, it buries me under its heaviness.

It is 辛い when I had my life painted around your being. It is 辛い when what I saw were things I've always wanted to share with you but now can never do so. It is a really unique 辛い that exists in me when I know they were all mirages of my own yearning. They will never be real.

For whatever reason, I feel appreciative of this word. I'm unsure why either but having something illustrate your deepest feelings so on point gives you a special sense of comfort. Ah, I'm not alone. Maybe that's what I feel.