MAP, I think we're talking apples and oranges here. What you're describing is situational depression, and everyone goes through it to some extent at one time or another in their lives. Clinical depression is something else entirely. It is a medical condition.
Consider it like diabetes. You find your blood sugars are creeping up, and you decide to change your diet, lose weight, and exercise regularly. Your blood sugars are back to normal. YOU have confronted the problem in your life and taken steps to solve that problem. Some people have a type of diabetes that destroys the cells in the pancreas that produce insulin. No amount of diet or exercise will help. They HAVE to take medication. Same thing with clinical depression. It's not the problems in your life that are "getting you down," it's the chemicals in your brain.
When someone is clinically depressed, it doesn't matter if there are problems in your life or if everything's going great. You will still be depressed.