I think some people might be mis-defining true depression. Everyone has blue days, true. Everyone has bad moods sometimes. Depression is different. Depression is due to a chemical imbalance in the brain. It isn't just a matter of getting the endorphins flowing. It's great that exercise works for you and others, and I am certainly not trying to start a fight, but I think it is disingenuous to tell people that if they just get some exercise they will no longer be depressed. It might lift their mood, but true depression is much more than that.