Don't Install If You Don't Have a Spare Apple Watch
If you don't have a spare Apple Watch to install the watchOS 6 beta on, you should avoid the beta. Apple offers the developer watchOS 6 beta so that app developers can test their apps on an actual Apple Watch with the new software.
These developers typically have a spare Apple Watch that is dedicated to testing. This is especially important for the first few Apple Watch betas that can be more problematic.
If you've been testing on an old Apple Watch, you may be out of luck since Apple dropped support for the first Apple Watch last year.
You may be able to find a cheap Apple Watch on eBay or Craigslist if you need one just for testing this update out. You can link two Apple Watches to the same iPhone.