I'm pretty much the exact same way. Although I tend to focus more on the being a "smart-***" route. I think it's just because if you have dealt with so much negative, you tend to project it quite a bit.
I tend to have a much...darker... perspective with life. The whole "Im not a pessimist, I'm a realist" attitude. I tend to find people who are overly optimistic well.. annoying. Yet I feel I don't do it to be mean, it's just a result of cause and effect. Again, I try to put it as smart *** sarcasm than straight bluntness so I don't come off as a jerk. Kind of a House attitude.

We try to downplay things because it probably helps our world outlook in our minds. Because if thing's go well for others but not ourselves... we obviously feel bad about it. It can also lead to feelings of envy and/or jealousy. It's something I still deal with.

Deep down we just want the world to cut US a break for a change.

Another thing to point out is we try to keep ourselves level... sort of restrain from elevating our mood to an extent. The higher the rise of good feeling... the further the drop we can experience of bad.