THIS is one of the best articles you'll read on depression.
7 Big, Stupid, Destructive Lies Depression Tells You. It begins with “Depression is a beast. It's an illness so insidious that sometimes you don't realize the scope of its life-threatening power until you're drowning under its waves.”
You will recognize some of these lies. Such as “You're not trying hard enough.” You may tell yourself these lies all the time, and not even realize it's the depression talking!