For me, one particular LTR comes to mind. The way this woman serviced and looked after me was unprecedented in my world. During intimate moments or even sometimes just cuddling on the couch, she would just stare at me with those massive dreamy puppy dog eyes. Emitting a youthful glow. Nothing short of infatuation. The feeling I would receive from this felt primordial. It would just break me, make me weak and loose frame. I'd fall for it so hard that I felt I could truly entertain the idea of a Romeo and Juliette situation. To me, that felt like genuine desire... While it lasted. It's almost unmeasurable the joy and satisfaction you can experience from some women.
I have been lucky enough to experience this a few times. When it's a woman you find beautiful, and everything else seems to check out, it's close to indescribable and frankly almost irresistible for any man except the darkest triad mfers. In effect, she gives chase.
Imagine a woman you think is smoking hot, with all the fundamentals, making an effort to stay in contact even when apart, bringing you little gifts, asking about you and listening intently to your responses with genuine interest, and always insisting on being in contact with you. She learns what you like and at what levels and delivers on every front.
She sees you in everything, and (if you're lucky) you see her in everything; you do things for each other because you also feel a genuine desire for them.
Gentlemen, it's like crack. And then one day, suddenly, it stops, cold, and you're left standing there wondering wtf happened, and she's gone from your life.
Women (most) are fickle and will lose interest due to the most insignificant issues they can build up into massive things. For those who have been lucky enough to experience the above for several years, you're lucky; the longest I've been able to maintain that level of effort from a woman was three years. Either they change their behavior into something you no longer want or just have a psychotic break, and you dump them or they you.
YMMV