1. "She'll be happy there. Because she wants to be happy there." The context of this comment was someone's daughter being accepted into her first choice of college but when you think about it - there's such applicable universal truth to this simple statement. Apply it to your college experience, your job, your relationships - when you *want* to be happy, it's so much easier to be happy.
2. "Things are never as good or as bad as they seem." I actually forget the original context of this one. And in the years since I've heard it, I've applied it to both the good situations and the bad. To stay even, and avoid dizzying elation as well as temporary hopelessness is a valuable life skill.