This is a point that is often missed in the conversation about depression. In the middle of a major depression, literally nothing you can say to the person will cheer them up. The best you can do is be near them, express love, and try to help them maintain sleep/eating/exercise and therapy.

    no matter what most people tell you, your 
    brain will find a way to use it to dig the 
    hole deeper.

"I've got them fooled. I'm a fraud, they just don't know it."

"They're just being nice."

"This good person's kind words and actions are wasted on a piece of crap like me. If I wasn't around, they could 'spend' that kindness on somebody who actually deserves it. I'm hurting the world just by being here."

"They're lying, and now I feel worse because they're lying"

"I hurt so bad inside, and it hurts so bad to wear this mask and graciously accept the praise"

"I hurt so bad inside that I wasn't able to accept the praise graciously, and now I actually feel even worse because I've been so rude to this nice person who praised me"

Yeah. It's a struggle.

Even when you logically know those things are false and it's "just the depression talking" it's very hard to break out of those thought patterns.

(Which is why practicing positivity and gratitude -- keeping a gratitude journal, etc -- is actually an effective part of treatment for me. I'm not sure if it's because of specific neuronal pathways being reinforced by specific repeated thought patterns or what but, from a practical perspective, I try to treat positivity like a muscle that I need to exercise)