There is not one writer who never needs an editor. We once edited a manuscript 85,000 words in length. Simply taking out non-essential instances of the word “that” decreased the manuscript by almost 3000 words. This writer was also in love with “just”. Our edit of that one word decreased word count by another 1500.
“That” is only a powerful word when used where it does the most good, such as in differentiating between two items when those two are close in time or space in the story. Too many writers use “that” when they instead could use the, a, it, and so forth. Give it a try and see if your manuscript doesn’t benefit.