I recall something said by a famous architect, a Los Angeles-based one, I think. It could have been John Lautner, but really, I don't remember. I'm going to try to paraphrase it from memory here:
If you've got a great idea and are hoarding it, saving it for that big project that will someday come along, your stinginess will stunt your creative growth and you'll be forever waiting for the big project. Be a spendthrift with your ideas, use every good one as it comes along, even for minor and "unimportant" projects, and the good ideas will flow like water; you will succeed and your reputation will grow and the big projects will come sooner and you'll have plenty of good ideas for them.
I imagine that must be true for other artists, too. That way of creating, resisting the temptation to squeeze every last drop of life from successful formulas and relentlessly moving forward helped set the Beatles apart from every other musical act of their time, and I bet it might apply pretty well to writers, too.