Change just one vowel, and you might change a word completely. Some homonym pairs are similar right down to a single letter. Swap the letter out for a different one, and you've just changed the word -- and with it, your entire sentence. If you don't use the words that complement your story correctly, no one's likely to compliment your work. They're just going to be focusing on the errors, and that will disrupt the entire flow of the book.
Some word pairs are a little trickier than others because they're just too similar, and spell checkers will mark both as correct. Here's the problem: the meanings aren't similar at all, so if you use the wrong word you're just making a mess of your writing.
Complement and compliment are confused all the time; they're especially tricky. To compliment someone is to praise them. When you says "hey, Linda, you look great today," you're paying Linda a compliment. But if you complement Linda, it means that you complete her. A skirt Linda's wearing might really complement her legs, but if you remark on that skirt then you're complimenting it.
Tricky, right? When you have trouble knowing which word goes where, just swap it with a synonym. Instead of compliment with an i, change the word to praise and see how that fits. Change complement with an e to enhance and re-read the sentence. If it still makes sense, you've got the right word. If it doesn't, change your vowels.
Stationary and stationery exist only to cause trouble for writers. One means to stay in place, and the other is personalized mailing equipment. You may think you're never going to use either word, but as a writer shouldn't it be your goal to use all the words? At the very least, you ought to know how they can be used.
Stationary means to simply stand still; Mount Rushmore is a stationary object. Stationery is the pretty paper and matching envelopes you use to write out your party invitations, or whatever. Remember that e goes with mail (like email or envelopes) and that a stays in place, and it can help you remember which one to use when.