“The thing you’re creating isn’t necessarily yours.” Andrew Navaro, Art Director, Fantasy Flight Games
There’s a natural tendency to be protective of your play.
If you’re doing it right, then it’s something that comes from within you, that’s yours, that speaks to others of the creator that you are. To paraphrase Dr. Seuss, there’s nobody out there more you-er than you, and there’s no one else who could create exactly the same things you create.
The trouble comes from the fact that you’re not just playing for you.
You’re playing for, and sometimes with, others.
That means you need to keep them in mind, whether as the audience of your product once you’ve completed it or as the fellow members of a team building something that your play is going to be a part of.