Depression is identified by its symptoms. A common attribute is sadness. When people have an ordinary mood swing they'll say they are depressed. But if it lasts for over two weeks and you "can't pull yourself up by your own bootstraps" then it may be a symptom of a disorder. At that point it is good to seek help. Otherwise it may go on for week after week, month after month, and year after year. That kind of prolonged problem is called a clinical depression because it requires treatment. Symptoms persist and strongly affect thinking, feelings and behavior. They can become so disabling that they interfere with the ability to work, sleep, eat, and enjoy once pleasurable activities. But not all symptoms may be present and their severity may vary. Serious manifestations may indicate a major depression. Less severe signs may point to dysthymia which is chronic, though manageable, but will prevent you from functioning at full potential and make you susceptible to further depression.