I think these excerpts from A40YOV's unrequited love post, the 1st from A40YOV's post and 2nd from a responding comment, help point to why:
A40YOV: "I came to realize that she was the most wonderful and beautiful girl in the entire world, and there was not a single other person on the entire planet that I could imagine spending the rest of my life with besides Jenny. . . . My relationship with Jenny was a major turning point in my life. I learned about how great it felt to be in love and how horrible it felt for the love not to be returned. Ever since, I have been haunted with the desire to experience that feeling of love again."
Tammy's guy: "I'm almost 40 now and I'm still looking for that one true love that will return the love back. Since Tammy, like the author of this blog, I've been searching to feel that way again, but to no avail. Now, I feel myself regressing back to the emptiness of daily existence like it was before Tammy came into my life. And I'm fighting hard to resist it, but it's getting difficult by the day. . . . the older I get, the more I feel it's becoming too late."
Traci brought into my life a world of hope and happiness in which I could see the coming decades with my wife and mother of my children guiding my life's decisions. Fate seemed to bring us together in Korea, not as it turned out, mere - extraordinary - coincidence. I'm not saying I went shopping for an engagement ring following the first sunrise we watched together, but I could see the road leading there. Turning away from that dazzling promise and falling back to the dark alone feels a little like dying.
I don't think I've been holding out for a 20-year-old Traci to somehow come to life from my memories, change her mind, and whisper into my arms. My head knows better. Rather, I think my heart meant to protect me. I'm afraid Traci was my one chance for fulfilling happiness, so my heart decided it was better to hold onto the dim light of a lost love defined by sorrow than to accept the dark "emptiness of daily existence" without her.
It has hurt to keep Traci in my heart, but it hurts more to let her go. Part of me simply is still in love with her. But, the fact is my life will be without her, and I've paid a price for protecting a dead dream. I depend on feeling ("introverted feeling", in Myer-Briggs speak), which comes from the heart. I wonder how my heart holding onto Traci has affected my feeling and thus my life over-all. What greater price have I paid for falling in love with a girl who didn't love me back? I need my heart freed in order to live my life the best I can. Who knows - Traci fatefully entered my life a short time after I let go of Judy. Maybe that means letting go of Traci will allow a new love to enter my life. I don't believe I'll experience beauty like Traci's again, but I have to believe I'll fall in love again.
Stand down, my heart. You fought the good fight and did what I asked of you. It's time to let her go.