Bipolar disorder is not a single disorder, but a category of mood disorders defined by the presence of one or more episodes of abnormally elevated mood where you're feeling like the you're in Superman (clinically referred to as mania) and depression where you're feeling like you're the most worthless person in the world. These episodes are normally separated by periods of normal mood, but in some patients, depression and mania may rapidly alternate, known as rapid cycling.
Bipolar behavior is usually characterized with emotional inconsistency not seen since PMS. In any case, two particular stages of bipolar disorder happen the longest, and they're called mania and depression. Hypomania (either a burst of pure excitement and elation or, more rarer, a blunted feeling of apathy), also occurs, but is usually short-lived. During this time, the bipolar person is in his best behavior.
Now, onto the main stages of this disorder. The behavior of a bipolar person during the stage of mania is just as the name suggests. The person is manic. The person is jittery and seems to feel no fatigue. A bipolar person in this state keeps constantly active, burning up the hours with countless activities, and taking no time to rest.
After this string of energy-filled activity, the person burns out. Then the next stage kicks in. When a person shifts to the stage of depression, all the fatigue that he or she should have felt in the mania days kick in. The person then behaves in a way of a loner.
In the depressed phase, a person becomes a wallowing recluse. He or she experiences feeling of self-hatred, regret, anger, sadness and any other negative emotion that may arise. These feeling last for longer than the mania.
Once this down state ends, the person goes back to either the hypomanic state or the more dangerous manic state. This self-destructive cycle usually repeats itself until the person couldn't take it anymore, often leading to suicide. This type of disorder should be acknowledged and treated as soon as possible, because without treatment there's only one other way for a bipolar person to escape his see-saw of emotions.