As a discovery writer, the most important thing is being open to discovering your story as you write. The first draft is just the beginning - you may find you need to change your story extensively in subsequent drafts before it fully takes shape. Do not panic. This is normal for a discovery writer. Just relax. Do the writer meditation. Stare out the window for fifteen minutes and daydream. Take a nap on the sofa. Have a drink if necessary—whatever you need to relax. You will go the wrong way many times in your first draft.
Trust that the act of writing itself will help you find the heart of your story. Don't feel discouraged if you need to rework plot points, add or cut characters, or even take the story in a new direction in later drafts. Every word you put down brings you one step closer to knowing the story you want to tell.
The key is not to get too attached to any one version. Be
flexible and willing to make major changes if needed. Adhere to the philosophy
that you can't fully know what you mean until you see what you've written. Let
the story emerge organically through revision after revision. Eventually it
will come into focus.
So keep an open mind as you write that first draft. Don't worry
about getting it perfect. Just get the basics down. There will be time later to
shape it into the story you envision in your revision. Trust the process of
discovery through writing. Your story is in there waiting to be found.