My watch suddenly discharges in approximately 3 hours
Is there a process to fix the power use of my watch
Watch uses a LOT of battery
First check for damaged battery...
Charge the watch to 100% at bedtime.
Take it off charge,
Turn it OFF - hold in side button til you see the sliders and tap the tiny off button, top right. Confirm off with slider.
Leave it off charge and turned off til morning
In the morning turn it back on and it should be at least 98%. If NOT then the battery is damaged.
Force restart your watch and make sure to turn off background app refresh and check walkie talkie is not accidentally turned on.
Test the watch for a day.
Then if no better
If the battery is OK then unpair the watch and then pair it again.
Unpair and erase your Apple Watch
If it still discharges unpair it and pair it again without restoring the backup.
Check that the iPhone is not using any security apps or VPN that can affect apps on the Watch. You don't need any of them and they can be incompatible with iOS16 on the phone.
see also
Batteries - Maximising Performance - Apple