Another quote from Jim Carey:

  People talk about depression all the time.

  The difference between depression and sadness is sadness is just, you know, from happen stance. Whatever happened or didn't happen for you...

  ... and depression is your body saying fuck you, I don't want to be this character anymore, I don't want to hold up this avatar that you've created in the world. It's too much for me.

  So, a friend of mine who's a spiritual teacher has a really good take. His name is Jeff Foster, and his take on it is that they should change [how we think of] the word "depressed" as "deep rest"

  deep rest - your body needs to be depressed, It needs deep rest from the character that you've been trying to play.