We tend to think the payoff for writing a book is getting it into the hands of readers, and the payoff for writing screenplays is seeing your work on a screen, small or large. That's not wrong, especially if you're hoping for a financial payoff.
But novelist Anne Lamott has another angle to consider, one that I feel more connected to these days:
“I just try to warn people who hope to get published that publication is not all that it is cracked up to be. But writing is. Writing has so much to give, so much to teach, so many surprises. That thing you had to force yourself to do — the actual act of writing — turns out to be the best part.”
I know exactly the reaction I would have had to this quote before I had anything published or produced: "Easy for you to say, Anne Lamott! You've had books published and you're famous(ish)! Don't worry, I'll deal with the disappointments if they happen, just let somebody produce one of my scripts--or at least buy one!"
I'm not suggesting that you should lose any of that drive or ambition--it's necessary for a writing career. I only want to say there's more than that, and the joy of writing can get lost if you're putting all of your focus on worrying about what happens to it afterward.
The reason I feel more connected to the rewards of writing for its own sake is that over the course of a difficult 18 months, health-wise (much better, now, thanks), I still had the drive to write, even if only short films and scenes that I wrote without thinking about whether they would ever be submitted anywhere, much less produced or published.
Now I'm getting back to writing scripts for which I have commercial ambitions, but with a greater appreciation of what a friendly, healing presence writing can be.