Chin Up: Depression

A depressed person cannot put their chin up and just be happy. You can say to them "But you're loved, you have a job, a good life, family and friends" and that won't change anything. Someone who is down because of a job loss, bereavement or relationship problems has a reason to be down and they are down not depressed.
Depression does not care whether you are ugly or pretty, fat or thin, poor or rich. 
As Stephen Fry claims, mood is like the weather. It can change, it will get better, it cannot be controlled.
Depression is the thunderstorm, the rain, the snow. Happiness is the sunshine. 
Bipolar disorder/manic depression is the two extremes of moods. The dark dismal depression, where everything is rubbish and life is not worth living, and then the mania - when you are filled with thoughts and ideas, you believe you can solve the world's problems, become famous, write a book, you have loads of energy and cannot stay still, your mood elevates.
There is no point in getting annoyed at a depressed person for being depressed.
You wouldn't get annoyed at someone for having heart disease or cancer. There's no reason for someone to have cancer, just like there is no reason for someone to have depression. They just do.

                                         Stephen Fry talking about bipolar disorder

If you know someone who’s depressed, please resolve to never 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 they’re going through. Be there for them when they come through the other side.
It’s hard to be a friend to someone who’s depressed, but it’s one of the kindest, noblest, and best things you’ll ever do.
-Stephen Fry

http://www.huffingtonpost.co.uk/2013/08/23/best-and-worst-things-depression-help_n_3802904.html