Why you don't need to worry about your ideas leaving the building
Sometimes the fear and pressure are sneaky. They push you to go work really hard on finishing—or they push you to jump ship and go explore a new idea. What you're really feeling is fear that your ideas are going to go somewhere else—like they'll run off and shack up with someone else—or that you aren't capable of doing them right, making them into a beautiful baby.
It might help you to realize that most of your ideas come from somewhere else.
Most of them aren't yours, anyway, and they never were.
Because of that, maybe you can relax about "letting them down."
If they're tired of waiting, they can choose to go somewhere else. Nothing lost, nothing gained. They were never "yours" anyway.
But for the most part, ideas are incredibly patient. I've had ideas wait around for me for years, patiently biding their time until I was ready.
The other thing I want you to know is: They chose you for a reason.
They chose you because they really, really like your style, and they know you will do them right.
So they don't really like to go find someone new—it's too much work and they're invested in you, too.
So relax and breathe, and trust that they will be there waiting when you are ready.