Hi all,
I too have experienced this issue with my Apple Watch 4 since the new upgrades came out. I have an iPhone XS that it’s paired to. I have done as julieda has suggested repeatedly; it works for awhile, but at some point, the drain resumes.
I looked through the diagnostic logs (Apple Watch app on iPhone, General, then scroll to the very bottom to see Diagnostics Logs). I didn’t make a copy of it, but I found where the Reminder daemon was consuming too much processing capacity.
Then I tried an experiment. For a day, I deleted the Reminders app from my phone, which also removes it from the Watch. Then I did the reset julieda mentions. Battery life dramatically improved. With Reminder installed, I got between 2–3 hours of Standby. With the app removed, I’ve returned to the usual 10–11 Standby hours. I tried this experiment a few times and got consistent results. I’ve since left Reminders off my phone.
I can’t say that this works for everyone, but it did in my case. Unfortunate, though, I actually like the app. I’ll submit feedback to Apple accordingly.
By the way, removing Reminders from your phone won’t delete the contents, since they’re stored in your iCloud account, assuming synch wasn’t turned off.
If you give this a try, I hope it works for you as well.