I really do wish people the best that I have dated. I want to see them happy and content and blessed. Aside from my last relationship, I get along with everyone I have ever dated.
I feel like the difference between working it out and staying vs. Letting go has to do with where the people in the relationship's compass is pointed. Sometimes people put their ships together but, are headed to completely different continents.
In MBTI terms it would be their Temperment. (NF,NT,SP,SJ)
In social terms it would be that some people strive to fit into society and become productive responsible citizens. Some people want to be free of society and be unproductive irresponsible citizens. Some people value human interaction and need to feel connected to people. Some people prefer ideas, objects, toys, books and in general feel uncomfortable around people.
Some people value tradition and long for the environment that each holiday and season possesses. They love the warm Autumn colors, The smell of a Christmas Tree, hiding Easter eggs amidst springs first flowers and all the birthday parties in between. Some people don't like having to change everything every 2 months, they don't like jumping through all of the hoops of trying to keep up with every event that happens on a calendar.
The other big factor is the expectations from previous relationships and the culture we grew up in. First relationship expectations can be positive, which sets a high standard for others to follow, or they can be negative, which might lead to poor relationships in the future. If people have been told that they are ugly or they have been cheated on or abused, sometimes they can't have a good relationship with a good person because its not what they are used to. They might create drama to fight and feel wanted or so that no one gets too close to hurt them anymore.
Great relationships can be a sort of curse too. Being really close to someone and having that connection doesn't come easy. And when the new relationship comes along, there is an urge to strive for that level of depth and communication, but it may not be possible(see compass) and even when it is, it takes time and trust.