It's really a metaphorical "tumor" that presses on your brain every day and makes sure that by the end of that day, you are once again reassured that you are the most worthless, hideous, disappointing monstrosity to ever walk the earth. That is what depression does to you. That is what depression is: a tumor of emotion.
If you know someone who's depressed please resolve never to ask them why. Depression isn't a straightforward response to a bad situation, depression just is, like the weather. Try to understand the blackness, lethargy, hopelessness and loneliness the're going through. Be there for when they come through the otherside. It's hard to be a friend to someone who's depressed, but it is one of the kindest, noblest and best things you will ever do. - Stephen Fry
Depression...real depression, not acute sadness, is a chemical imbalance. Mental turmoil is just as serious as the physical turmoil of illness. Address it.