Waiting until the next day to talk to someone who upsets you, for example, can be really good. You'll have the chance to calm down and you'll be better able to defend and express yourself.
Keep some perspective. Think about the situation that's happening around you and think about how it affects your life. Is it really as big a deal as it seems or is it really only going to set you off a little. Compare it to other problems that people might have, like getting cancer or having your house flood. Is it really that big a deal? No? Then don't sweat it. Learning to let the small things slide off of you can really make a huge difference in how you experience your life.