If you think grammar is something you only need in school, you#039;ll be surprised to find out messing it up can sometimes cost millions of dollars or make a huge difference in your personal life. Misplacing a comma, for instance, can change the meaning of a sentence dramatically. For example, note the difference between ldquo;Letrsquo;s eat (comma) Granny!rdquo; and ldquo;Letrsquo;s eat Granny!rdquo;