From a Washington Post column by Florence Hazrat about her book “An Admirable Point: A brief history of the exclamation point”:

Open your text messages. Scroll through a couple of threads with your close friends. Chances are you will find plenty of ! or !!! — to express anger or enthusiasm or sometimes just to lighten the mood. But in some contexts — in a note, say, to your boss or your mother-in-law — an ! might come off as too forceful or pushy or naively joyful. The Chicago Manual of Style says the punctuation should be used “sparingly to be effective.” But what does “sparingly” mean in our emphatic times? If you’re confused, you’re not alone; the exclamation point (or mark) has long been a source of confusion and contention. Naturally!