[SOAPBOX]
Duality
Why Right And Wrong, Negative And Positive Are Bullshit Values
Or, well, maybe that statement is a little harsh - they are not bullshit as such, they're subjective, true, but even on that level they have little absolute good/bad value. Anyone who knows the concept of duality will know that without anger, love would be worth less (or even worthless). It's a simple mechanism - one gets used to what one is always around. In short, eternity is the last thing you want to spend in a one-sided place like heaven or hell.
I love my anger, sadness and despair - primarily in retrospect of a situation of course, but also sometimes during it, when I feel just how powerful these emotions are, and what they mean and what they allow me to do in future (be happy). The only emotion I consider useless is shame.
The values that are important with emotions are their strength. And all emotions can be strong, given that they are not supressed needlessly. Whether it's a "good" emotion or a "bad" emotion, they allow each other to be more intense the more you let them oppose each other - an inner rivalry that is the essence of being alive. :)