People tell you to write your most important story, your most vital book to share with the world.
I get that.
They're trying to impress upon you the urgency you need to write, and to ensure you don't waste your time or other people's with what you're writing.
But my advice goes against the grain: Don't focus on your first book being your best, a masterpiece debut. It's getting so many of you hung up and freaked out.
Save your "best" stories for your 3rd or 4th book in, so that you'll have had practice along the way and understand what goes into a good book, and what doesn't.
There are a few people who only make one book in their life. Some people who also get lucky and write their very best book first. But I don't see why that's something real human writers need to aspire to. In practical application it leads to so much kitchen-sinking in first novels and poetry collections, the results are often clunky and embarrassing.
So, seriously: Try making a few good practice collections first, before going for your magnum opus. It'll do you good.