There should come a point in every romance novel when a reader hugs the book to her chest and sighs. Or something like that. Something that demonstrates the reader is emotionally invested in the characters and their Happily Ever After.
I just finished a book where that didn't happen for me. Like, not even close. I kept waiting for that big moment. I kept hoping it would happen, that something in the book would reveal itself.
What is that something?
Two words: High stakes.
If the idea of the hero and heroine not ending up together just makes a reader shrug and say, "Meh," then your stakes are not high enough.
It's not enough that they end up together. Romance readers already expect that. But if you want to craft a story that makes them sigh -- or, even better, cry -- when your characters end up together, you need to make the alternative truly awful.
Aks yourself this: What is the worst thing that could happen to your character if they don't end up with the love interest at the end of their journey? If it's really not that bad, your stakes are not high enough.