If you’re writing anything of any importance get at least one other person to proofread it.
Yes, you can proofread your own work (and you should!), but nothing beats a different pair of eyes. Different eyes are attached to a different brain, and that brain is filled with different thoughts, emotions, and perspectives. Those differences will lead to commentary, insights, and revelations you simply cannot have on your own.
You are simply too close to your own writing to proofread it as effectively as someone else can. You often can’t see the forest for the trees, which means you’re going to miss small things like typos and big things like forgetting to remove several sentences you thought you removed yesterday.
Writing is difficult. It gets easier the more you do it, but you’ll never master it. You’ll never reach a point where your words won’t benefit from someone else reading them. Even professional authors with dozens of popular books have proofreaders look at their work before publication. My wife, Aleen, proofreads every single one of these tips before they’re published. Her input has been instrumental to the level of quality and utility you see here at Core Assistance.
Oh, and one last thing: When you find a good proofreader, show your gratitude. Tell them how awesome they are, and do so frequently. Take them to lunch. Pay them. Whatever the arrangement is, make sure you show them how much you appreciate them because a good proofreader is rare and incredibly valuable.