When most people hear "bipolar", they think of a moody person.  Sometimes they're unusually happy, sometimes they're the opposite.  That's one of the reasons it can be so difficult to get people to take bipolar disorder seriously.  Mania is not happiness, and depression is not unhappiness.  Whereas happiness and unhappiness are normal, mania and depression are not, and they can mess your life up before you even realize it happened.  You're also usually the last person to know if you have either, so make sure and pay attention to what people have to say.