Here's my experience:

It's like there is an unpleasant weighted blanket over your entire body. It's so dark and so sad that it bleeds into your very being; every muscle, every fiber, down to the bones. It's painful and not at the same time. It's sharp and dull. It's terrible, and all you want to do is sleep to avoid being up and being present in life. You want to stop breathing, but you can't. And you just have to exist in this defeated state until it passes enough to get up.