I have lots I've been given over the years that have served me well, but the one I probably use most often is "Worry is like a rocking chair, it gives you something to do but it gets you nowhere". I've learned to be really good at not worrying about stuff, so I tend to pass that one out more these days.
And also this one that I saw online somewhere, "If someone doesn't have your phone number, then they aren't important enough to have an opinion about you" I tell myself that one daily when someone at work starts to annoy me