Happy endings (or unhappy one for that matter) can’t be gifts to the character. They can’t be happenstance or the result of someone else’s actions or choices. They can’t occur because the character happened to be in the right place at the right time. They must be the result of something the character did.
I was reminded of this recently when reading an early draft by a fellow writer. In chapter 1, the couple meets. In chapter 6, the hero thinks she’s the one. For me, this qualifies as insta-love.
For those of you who aren’t familiar with the term, insta-love is when two characters in a romance fall in love too quickly. Insta-attraction, insta-like, insta-lust are all okay, but insta-love? Not so much.
Like happy endings, love has to be earned. It’s earned in little moments as the two get to know and trust each other. It’s earned when he holds her while she cries or when she keeps his secrets or takes care of him when he’s sick.
Insta-love is too much like that guy who wants to get laid and doesn’t care who the woman is. All he’s looking for is a warm body. In a romance, you don't want readers to feel like the heroine is the warm body who happened to be at the right place at the right time. The reader needs to feel the this is the woman he'd have searched his whole life for.
So that's two things your characters have to earn. Love and happy endings.