The happy ending cannot come in the middle of the story.
3 seconds sound clip from the The Last Unicorn movie soundboard.
You can hear this line at 01:22:39.505 in the Blu-ray version of the movie.
Quote context
[...]
- I don't think I could change her back even if you wished it.
- Marry the prince and live happily ever after.
- No. Lady, I am a hero, and heroes know that things must happen when it is time for them to happen.
- A quest may not simply be abandoned.
- Unicorns may go unrescued for a long time, but not forever.
- The happy ending cannot come in the middle of the story.
- But what if there isn't a happy ending at all?
- There are no happy endings, because nothing ends.
- Schmendrick, let her stay the way she is. Let her be.
- That's not in the story. Lir knows that, and so does she.
[...]