The sudden realization that I was in love. I have loved and do love, but was only 'in love' once. It came in a moment; one minute my girl was simply "my girl friend," the next, the woman I wanted to spend the rest of my life with. It didn't happen. Engaged, jilted for another guy, I felt the angst for a long, long time.
Later, much later, I realized that we are not in love with another person, but with an 'idea' of a person we have fabricated in our minds. To be 'in love' is to be 'in need' and when we are in need of another to fulfill our lives we are very vunerable. We are, I believe, living in a very immature state at that time.
Now, I simply love the woman a who came along later...and we've been married for over fifty years.