The first iteration is just a draft. Get it done as quickly as possible. Don’t spend too much time on it.
It should be changeable. Nothing that can’t be added to or deleted.
That first draft is important – but not so important that it should take you until the project deadline.
Maybe your first draft is some bullet points. Maybe it’s a rough sketch.
The quicker you get it done the longer you’ll have to edit, to revise, to improve. Go through as many iterations as possible as quickly as possible.
Once the deadline hits you’re stuck with what you’ve done.
Don’t get stuck with the first draft.