As a founder, of course, I have mixed emotions. When you create a company, your job is to make sure it can one day succeed without you. Then eventually that one day comes and the celebration can be bittersweet.
I've seen this before firsthand and it always looks painful. It's easy to look at something from afar and think, "why not just let it go?" But seeing the pain of letting go time and time again makes it seem far more difficult....