That would be an interesting question, and probably all of us have asked it at least once. Am I depressed for a reason or I am just suffering from depression as a disease in its classical description? That is another good question that can take the shape of a whirlpool in our mind, begging for an answer.
Regardless if we are sad because something did not turn out as we expected or because our boss is a tyran and we cannot cope any longer with the pressure, regardless if we have a long-standing history of feeling blue, there are things that can be done to help you feel better. If you are able to identify what is causing the negative emotion, try to change it. If you cannot change it, think about accepting it. If you cannot find any cause on your own, talk to your dear ones that can better see the elephant in the room. Or, you can always turn to seek the help of a professional. No one should feel sad, hopeless, cornered, when help is available.