Just like the iPhone, Apple added a way to hard reset the Watch in a similar manner. If your Apple Watch freezes for any reason, simply hold down the Digital Crown and sleep button for about 10 seconds. The screen will go dark after about 5 seconds, but keep holding until the Apple logo appears on the screen.
After the aforementioned process, the Apple Watch should be completely rebooted and hopefully won't cause any other problems. Like we said before, it's a first generation device, Apple is still collecting feedback from Apple Watch owners to fix any overlooked issues.