I don't why you are so insistant on using the word "disease" to describe depression. It's a disorder, not a disease. My point about mania is that there is a spectrum of mood disorders, again pointing to the fact that it's not a disease but disorder

You don't always feel like shit for a reason (or at least a good reason). Like when I was younger, I didn't have a reason to feel shitty, but I did. And shitty isn't really the best word. Life is just ridiculously gray and dull and nothing seems worth doing