How do you know when your product is done and ready to launch?

I think a-lot of us, because we put so much effort, should if you will, into our products that it's hard to know when it's done and when it's ready to launch. So much gets said about MVPs, focus, and just getting it out there, but I'm curious to know what is your internal barometer for knowing when your product is ready and you should just get it out there?