Exclamations are fantastic for e-mail, and possibly for texts, but when you're writing a novel, use them only for interjections (hey! ow! zoinks!). But just in case you don't think I have enough clout to boss you around, let me pull out a bigger gun.
"Cut out all those exclamation marks.
An exclamation mark is like laughing at your own joke."
~ F. Scott Fitzgerald
This year instead of promising to lose 10 pounds (you know you won't) or swear you're going to cut out sugar and eat healthier (until the next slice of cheesecake comes along), allow me to suggest a resolve that's much easier to keep: use your words to make your emphasis instead of relying on a line and a dot.