I've been somewhat negative lately. For instance, today is my sister's birthday. I thought of nice things she's done for me, then immediately thought of the crappy things she's done to me.
I don't wallow in the negative, which would make me morose. I don't really get angry about it, which would make me a grudge-holder. I don't plan my revenge against her, which would make me vindictive.
It just briefly springs to mind, neutralizing the happy thought as acid neutralizes a base. That makes me a sourpuss.
And a bit cranky. In a, "Clean up that mess! Claire isn't coming over to play today unless you pick up all your clothes and put your books away! Go to bed! Dilf, stop touching my butt!" kind of way.
But the coffee's helping.
