Greetings, SmallFish24-.
Welcome to the Apple Support Communities. We can understand why you’d want to resolve the issue with your Apple Watch battery lasting for less time than expected.
First, Restart your iPhone and Restart your Apple Watch. Then, check out the following resource to learn about how to get the most out of your battery: Batteries - Maximizing Performance - Apple
If the issue continues, consider providing additional information.
- What types of apps do you use with your Apple Watch?
- Has anything changed with your usage?
We hope this helps! Thanks for being a part of the community.
Sincerely.