The magic of a first draft is that the first draft is always perfect. It doesn't matter if it's rubbish, if it's messy, if it doesn't flow, if it lacks personality, or if it won't work. The job of a first draft is to be a draft and get the process started. So however it turns out, the first draft has done its job perfectly.
In the illustrated art collection by Dr Seuss you can see some of the first drafts and iterations of text and images that go to refine the seemingly effortless rhythm, rhyme and combination of text and images from his wacky illustrations.
Donald Schön, in his classic The Reflective Practitioner, goes further by sharing his analysis of design as a reflective conversation – observing each mark sketched on paper informs the next you make. You don't know how it will turn out until you put pen to paper. Seeing what comes out allows you to adapt and modify as you go in a back-and-forth of discovery and evaluation.
Don't worry about your first draft — it'll be perfect.
I read this for the first time in an article by Casey Fowler that's no longer live. Most likely, it originates from the novelist Jane Smiley:
"Every first draft is perfect because all the first draft has to do is exist. It's perfect in its existence. The only way it could be imperfect would be to NOT exist."