Chronic depression- I've been dealing with it, on and off, since my teens. I'm 72. It does feel like carrying something heavy- Wil Wheaton is so right on with his descriptions. I admire him for talking about his mental health issues- he also seems like a heck of a nice guy.
After a zillion years of dealing with this I came to this realization- It's not negative thoughts that cause depression, it's depression that causes the negative thoughts. I believe it is a physical illness- it runs in my family, it's actually killed a couple of family members. I have no more reason than anyone else to feel sad- in fact I have a great life- but I notice that any amount of stress, even good stress, can cause a flare up. I go on and off meds and I make sure to exercise and maintain some sort of routine to keep it at bay. Exercise is so important and I am kind of worried that when I can't go and walk 4 miles a day, as I do now, that it will become intractable.
I have a 70 year old friend who gets ECT twice a year and that keeps hers at bay. I hope it doesn't come to that, but I'll do whatever I can because depression is torture. At least now it is approached medically as opposed to being considered some sort of failure of character. It's an illness, same as diabetes or any other chronic illness, and there are effective treatments out there. Best to anyone who is going though it, and if you want to commiserate give me a holler. I've gotten pretty good at handling it- I might even have useful advice (no promises on that, though!).