Once upon a time I had a teacher who was fond of saying (jokingly): "You're not stupid, you're just ignorant. But, boy! Are you ignorant!"
lxegirl, as much as you care for your friends and want their esteem, they're ignorant of what you're experiencing. Low mood for six months accompanied by inability to control emotions and near-spontaneous crying goes way beyond questions of personal fault.
I'm depressed, too. Just as Elana, I cannot "think positively" whenever I'd like, and even when I do, it's fleeting and is not self-reinforcing.
Friends are great for lots of things, but one has to recognize their limited ability to understand this illness. Some of them may be open to learning about depression; I hope they are.
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My dog

mastered the "fetch" command. He would communicate he wanted something, and I would fetch it.