According to this surprising new study, it appears that anger improves decision-making.
I can't say that it agrees with my trading experience. Anger breeds a desire for revenge and seeking revenge in the markets after a bad trade is usually one of the surest roads to ruin.
But I can see how low-level anger (how should we call it...irritation, aggravation) could focus the mind and help the trade-selection process. A moderately angry (quite the oxymoron) trader would presumably make fewer mistakes than a bored trader, one would think.