I find myself using the word "that" too much. How do you really know when you need that "that" word there? Like just now. I don't think I need "that" there. Do you have words you overuse?
Plenty of writers have little tics like this. You may find a turn of phrase that you just fall in love with, or it may be something that carries over from the way you speak. At various points in my life I've found myself overusing parataxis, 'although' and 'however', and probably a few others I can't think of off the top of my head.
To a certain extent, this is a matter of style. Only if a particular phrase or word is heavily overused, to the point where it becomes noticeable to the reader, is it a bad thing. However, there's no obvious line that you cross where style stops and bad writing begins. It's something you just have to keep your eye on.
You've already taken the first step by noticing that you frequently use a particular word. In some cases, you may not realize it until someone points it out.
My advice would be to not worry about it too much while you're writing. It's already in the back of your head. If you notice that you're really abusing it while you're in the process of writing, feel free to make some adjustments, but don't pause for half an hour just to decide if "this" is really necessary.
The best time to work on these tics is after you've written a chunk of prose. Go back through what you've written and look for the tic. All modern word processors have a Find feature (usually ctrl-F or command-F) that you can use to quickly find all examples of a particular word or phrase. As you edit, you can double-check each spot by trying to rewrite it without the word, and comparing it to the original.
If you really have a hard time deciding, it pays to have a few trusted readers who can take a look as well.
In editing hundreds (maybe thousands) of articles, I've found all authors have some kind of authorial tic: expressions that they use a lot, a tendency to use one verb tense over another, etc. Sometimes this is part of their personal voice; other times it's too much.
When you're writing, don't worry about it. Just get your thoughts written down on the page.
The time to remove your Needless Words is during the edit process. Nearly always I have to take out the word "really" from my own essays; that's the word I'm most likely to overuse.
Have you ever come across a website called autocrit.com into whose web forms you surrender your latest draft so that the site may return a list of excessivenesses from your prose: things like, “You used six initial ing words. Try to remove at least four”? Or “You had only two instances of that and four of was/were. Good job!”
In one writing forum, the algorithm got reviews along the lines of “don’t believe what it tells you” and “AutoCrit will ruin your writing!” I never purchased the large-scale AutoCrit service, but I feel okay surmising that it was less a prose killer than a tool that took care of CTRL+F for you and offered a statistical reminder of the line that @sjohnston was talking about in an earlier answer, an indistinct line separating style from unmindful recurrences.
I think it’s a good thing you do, watching out for that the pronoun, that the conjunction, even that the adjective and adverb. With so many uses for the little tyke, it in particular needs an eye (or an ear) on its lookout (or soundout).
If you want to know, if you use particular words too much, count them.
I gave one answer where I explain a revision process from Andreas Eschbach. At point four (marking filler words) you also can mark words like "that" or other suspicious candidates. When you have done that, count them and put that info into an Excel sheet. Over time you will see which word you use how often, especially compared to the other words.
If you find out, that you use "maybe" 1000 times when you used in the same text "perhaps" 10 times, then maybe you use "maybe" too often. You can decide , if you want to replace it with alternatives (like "perhaps" if appropriate) or just remove it.