It's possible you're thinking of a specific scene or episode that might have a similar theme.
To help me understand what you're thinking of, could you tell me more about:
* What kind of sacrifice are you thinking of? Was it a character's life, a powerful object, or something else?
* What episode do you think it was in?
* What season of Sailor Moon was it?
With more information, I might be able to help you find what you're looking for!