My wife and I were high school sweethearts and got married out of college. When people ask us how we made it work, I always say that during college we grew and changed together. We had hard times and we worked through it, as we learned and grew we worked together and compromised. We grew up together through college. When you have a long term partner, they soften your edges. I don't think people want to have their edges softened anymore, which makes compromise and sacrifice less and less common. Note that this is not to say you should just settle for anyone, but I don't believe we as humans are puzzle pieces.