I’m not saying that every sentence should be be delivered with emphasis. In fact, when everything has emphasis then essentially nothing does. But a little impact, wielded purposefully, can transform how a sentence is received.
“Reggie swung his leg in front of him and the kicked landed.” This is a functional sentence, but a flat one. It’s about a kick, but ironically it lacks any power. Or direction: What did Reggie kick?
“Clementine forgot her taekwondo belt so she had to go to the back of the line.” Perhaps this is exposition in preparation for a more exciting sentence.
“Alex overheard what the next test would be: breaking boards with a kick.” Okay, this seems straightforward enough. A transaction of information has been completed. The word “overheard” has some pull. Is something is being kept from Alex?
With relatively little effort, the exclamation mark can resolve these limp sentences. The tradeoff is subtly; the exclamation mark allows little of the quiet, open-ended wondering a fullstop might prompt – but sometimes that’s a good thing. When the sentences are all too quiet it’s hard to hear anything.
Let’s insert a little exclamation into these examples.