I realize that there are many people who have never experienced what I'm trying to describe, but it's not something that you just snap out of. And for the record, telling someone to cheer up is a really shitty thing to say to them. You don't just wake up one day with the sun shining and the birds chirping and suddenly all is right in your world.
It takes a long time to come out of this shit-- alive.
And it sucks.