When writing fiction, it is generally assumed that the first draft will not be your final draft. In fact, it is usually recommended that after finishing your first draft, you put it away for a while before returning to it with fresh eyes to take another look at it. The same holds true for writing content, whether technical or non-technical.
The reason for this is that while writing our first drafts, we don't really know what we're doing; we're still in the process of figuring it out.
Consider it similar to songwriting. You may have an idea of the type of song you want to write, the chord sequence you want to use, the time signature, and so on. However, the songwriting process is not always linear. Sometimes you just have to go with the flow and let the music lead you.
Only after you've finished composing that initial version of the song can you assess how closely it corresponds to the idea you had in your head. Does it perfectly capture what you wanted to convey? Does it deviate slightly from the original concept, and if so, in a good or bad way? Or is it such a creatively inspiring but drastic departure that the original idea itself needs to be scrapped in favour of something else?
Likewise, once we've gone through the arduous process of sweating out that first draft, it is important to get some critical distance from what we've written.
Why should I distance myself from my piece, you ask? This is due to the difficulty of having an objective measure of our writing while we are stuck in the writer's mindset. While you may have an idea of what the final draft of your piece should look like, it's difficult to objectively assess how close or far you are from your desired end goal when you're actively involved in the writing process.
This is why it's important to get that little bit of distance between yourself and your piece – perhaps go for a walk, wash the dishes, take a nap, brew some coffee, put on some music (not necessarily in that order) – and then return to take a fresh look at what's on the page.
This critical detachment allows you to examine what you've written from a calmer, more objective, and holistic standpoint. You can now evaluate how closely your piece corresponds to its desired end goal—how many objectives on your checklist it ticks off, whether it falls short of or exceeds its purpose, or whether what you thought was the final goal and purpose should be revised.
While this piece of advice may appear trivial, putting some distance between yourself and your writing can be crucial in being able to make these kinds of assessments objectively–assessments that are, in turn, crucial to the overall quality of your piece.