Getting an editor might seem like a luxury you can do without, but it is an integral part of writing.

This is due to the very nature of the writing process—you are writing, but your audience will be reading, and it is hard to put yourself in the position of the reader for something you wrote yourself. You know exactly what you're trying to express, and had likely gone through countless possible ways to put it in before picking one.

In contrast, your reader is reading it for the first (and, in all likelihood, only) time, and doesn't yet know what you're going to say. Couple that with the inherent difficulty of writing anything non-trivial in a way that's both understandable and pleasant to read, and a fundamental truth begins to emerge:

Writing is very, very difficult on its own. Writing and reading at the same time is just too difficult.

By way of personal experience, the first time I was exposed to professional editing was in the 2000s, during my university years; I was contracted by a large computer software and hardware vendor as a technical writer to write 5 or so articles for their online developer portal. The articles were to be an introductory series about a particular software toolkit I was very familiar with, aimed at programmers who were otherwise completely unfamiliar with the toolkit, and were supposed to be two thousand words apiece.

As a part of the writing process, I was expected to submit a draft to an editor, who'd then send me back an edited copy for any revisions. In many ways, working with an editor was a frustrating experience of culture shock. It's hard enough to fit anything technical in two thousand words; it's near impossible with an editor rewriting it to expand every single acronym, especially the ones you don't even think of as acronyms, like HTML.

But, at the same time, it was a thoroughly transformative experience. There I was, submitting a text I spent a long time on, agonising over how to convey all I knew to someone with none of the prior experience, in what felt like an impossibly tight word limit, to an editor who did not care what I went through to write it. Every time, they would unceremoniously drop a quarter of what I wrote, rewrite another quarter, and rearrange the remaining half, with no regard for my blood, sweat and tears. And every time, it made the text ten times better.

It also forced me to become a much better writer. I thought I was pretty good at writing before, but having an editor go over my output made me realise I was only capable of being pretty good at writing, and I had to pay attention to and consider what the edits I was seeing were telling me about my writing if I wanted to actually become good. I just didn't know what I was lacking until I started working with someone whose job it was to know those things.

And that's why you should always get an editor. It doesn't necessarily mean hiring a professional—it's great if you can get friends or family to do some editing for you. Just make sure you're getting someone who will be honest in their feedback—you want your editor to be courteous and constructive, but you don't want them to be nice and attempt to spare your feelings instead of fixing the text where it needs fixing.

Consider having multiple editors as well. If you hire me do two revisions of line edit for your manuscript, by all means, find someone else to do the copy edit and/or final proofreading. It's a great idea and I fully recommend that you do that. After all, by the third time I work on the same text, I have essentially become its co-author and will be subject to the same difficulties any other author would be.

P.S. I had this page edited before I published it, and my editor had me throw out 90% of the intro I wrote, and another paragraph entirely, which immediately made everything much better. Always get an editor!