Ever hit the CAPS LOCK key while you are typing? I have many a times. Therefore, I have a trick to make all the word back to lower case. You may just want to change the case to UPPER case to one or more words. You can do this without using the change case icon in the ribbon on the font group.
For one word, just sit anywhere in the word (you do not need to highlight it!) or highlight multiple words and then Shift-F3. The first time it will make the word(s) Uppercase. Do it again and it will make the word(s) Lowercase and the third time will make the word(s) Propercase. The cycle repeats itself.