So JK Rowling has admitted that she thinks she should have ended the Harry Potter series with Harry marrying Hermione, rather than Hermione marrying Harry’s best friend Ron.
“For reasons that have very little to do with literature and far more to do with me clinging to the plot as I first imagined it, Hermione ended up with Ron.”
It can be difficult, sometimes, to decide the fate of a character. You can be torn between what you want to see happen, what should happen, and what you think the reader might want to happen. Non-writers might not see how that could be possible – surely the writer creates the characters and is in control of their fate; able to pull different strings like some sort of creepy puppet master. Well yes, that is true (though I wouldn’t necessarily class myself as a creepy puppet master). The writer is in control. But the way you ultimately decide a story should go can be a hard one
That being said, I think you have to stick by your decision. You have to have the confidence to write your book the way you want to, and not suggest later on that you made a mistake because you were clinging to something that was wrong. There are so many possibilities when it comes to writing a story. The one you choose needs to be right.
For what it’s worth, I think Rowling got it right the first time in not pairing Harry with Hermione. It would just have been too obvious. Given the choice, I would much prefer to see a mismatched pair getting together and imagine how their life would go, whether the relationship was happy or unhappy. I would imagine Harry and Hermione’s life to be boringly annoyingly perfect. I think it’s best to deliberately do something the reader will not expect (or perhaps even dislike), providing it fits in with the rest of the story.