It's really tough when a relationship just can't hold together. It's especially sad when the two people continue to care for each other but the relationship just won't work.

I think people put too much onus on the "happily ever after" fantasy. No relationship is instantly perfect and no relationship remains static. It takes work. And sometimes, no matter how much work you put in, people are still independent of each other and constantly evolve, often in ways that lead them apart. That's not necessarily a failure. It's just a different course of evolution.