(I'm not talking about the one that tells you to stockpile an arsenal of guns).
You've written a script. You know it's good. You send it off to various companies. But nobody knows who you are. You're an untried writer. Back it comes again and again. Still you keep sending it out. Because you know it's good. The little voice in your head is hurt but unbowed by the rejections. All your friends and family keep saying: "You're not still sending out that script?" You ignore what everyone says.
Then one day, somebody reads your script and finds it funny. It's bought. It's produced. It's a massive hit. You're flavour of the month. Now everybody knows who you are. And knows how good you are. They want you to write another script.
Now you have the opposite problem. Everyone tells you how great your new script is. Your friends and family are falling over themselves to look at it. Everybody wants it to be great; they need it to be great. Only the little voice in your head tells you that the script isn't so great. It needs work. Or it needs to be scrapped. You ignore what everyone says.
The point is that as a writer you need to develop a little internal critical voice. A voice that is impervious to criticism or flattery. Of course as you develop, you also (hopefully) will have a couple of people whose opinion and advice you respect. But ultimately, you will still need the little voice in your head. The voice that you listen to.