You don't need to read any self-help books to know that shit happens. Sometimes it's minor, other times it's pretty bad, but inevitably, we can't control everything that happens to us. What we can control, though, is our response to it.
Notice, I chose the word response there, not reaction. There is a subtle difference in the word itself, but a huge difference in the action it describes.
Reacting is instinctual, where we say and do things we're not really in control of; we're not considering the implications of what we're doing. When we react, it's usually in a situation where we're tense, stressed and angry.

A response is thought through. Maybe you've played out a few scenarios in your head, weighed up the pros and cons. A response is usually more calm, collected and restrained.
Responding is taking a five minute break before replying to a difficult client, instead of reacting, by slamming down on the keyboard with passive aggressive comments immediately after receiving their email. And what makes a rash reaction worse, is that it usually prompts the same kind of reaction from other people! Then you've got a potentially explosive chain reaction on your hands.
When shit hits the fan, it's easy to get swept up in emotions which encourage a reaction. But do these hasty reactions showcase the best parts of us as a person? Do we want people to know us as someone who blows their top at the smallest problem? Sure, we all do this, but you actually have the choice of how a situation makes us act: will you react or respond?
Don't get me wrong, it's no specific science. More of an art, really. So in the hopes of creating a little less negativity in the world, next time something happens to you that provokes a reaction, take a quick second to decide how you want to respond. Do you want to yell, make yourself (and potentially someone else) feel worse, or could you simply take a breath, think 'whatever' and let it go? Does it really matter?
Sometimes, yes, it really does matter. But choosing to respond instead of react doesn't mean 'backing down' or letting something go. Quite the contrary, in fact choosing to respond with a mature and considered manner usually makes you the bigger person. And causes less stress in you and drama in your life.