Pretty sure a lot of people here have the same feeling. It's one I had before, and I still have after my success. There is always something else, something better you wish you had.
In my hometown, there is an entrepreneur; one everyone knows who started a 3D studio with now more than > 300 employees; a massive success. He lives in my neighborhood, so we happen to discuss from time to time on walks. He, at one point, stopped me when I told him how much I admired his work and how envious I was of his abilities to scale smoothly; he told me: "Phil, there is nothing I would love more than running a small profitable web business like yours with just two of my buddies."
When success hits for the first time, it's a disturbing feeling realizing your desires and insecurities are pretty much still all there. You are still an envious bag of meat.
Anyway, congrats Peter on the success and fantastic journey! Yes, I'm still a bit jealous, like most here :) But I work on this. I got to go; I got my Yin Yoga class in 20 minutes. It will surely help me realize how lucky I am to live a life of beauty and experiments. It will help me recognize this burning jealousy, accept it, as it is simply part of this beautiful game of life.
[1] https://missiveapp.com/blog/how-we-built-1m-arr-email-client