Try deleting all the third party apps and install it one by one. Give it a day before you install each app so you’d be able to figure out the culprit. The first time I used Sleep Cycle on my Watch it almost drained the battery to empty overnight. Some sleep tracking apps could cause this but there’s another user with good battery life who uses Autosleep. So I’m guessing it should be okay. --- Post Merged, Feb 4, 2019 --- My usage is usually about 20% of standby times and sometimes more like when I’m driving or working out. Have you tried the usual troubleshooting like turning off Background App Refresh or having some bad complication on the Watch face? Also while you’re at it, try disabling the Fall Detection and see if that’s causing the problem.