I have taken to saying: "Let your friends direct your movies" It is paraphrased from the parody song "The Star Wars That I Used To Know", by teddiefilms. Where the lyrics say "Have your friends direct your movies and they will turn out better" where it is saying that the Star Wars movies George Lucas didn't direct himself turned out better.
I think this is a very useful idea: that just because you started something, doesn't mean you are the best person to keep doing all of it. It particularly shows up around creating "things", someone has and idea makes a first version (or so) and lots of people get excited, the bussiness or community grows and eventually there are lots of people who can develop the idea further and better than the original creator, but they are hanging on longer they they should.
Example usage: - "Isn't it time you let your friends direct your movies?" - "Joe Smith is still designing every building his firm works on, he really needs to learn to let go and let his friends direct his movies". - "It's not like Bill Gates wrote the source code to Windows Vista, he learned long ago to let his friends direct his movies."
But being that this phrase is a reference to a parady song, i feel like it is too obsure so I am looking for a better alternative.