Back when I studied karate, my teacher occasionally tried to make me angry so that I would fight better. It never worked. I never do anything well when I'm angry.
Later, I figured out why: I get angry when I feel powerless, so I associate anger with the inability to do anything.
What actually works for me, in fighting or in doing almost anything, is staying calm. By calm I mean a peaceful centered feeling that allows me to take in everything going on around me without reacting emotionally.
I confess, I can't always find this feeling, especially on mornings when I've overslept, am late for work, and there are delays on the subway. Days like that I tend to rant and rail at the little things in life that drive us all crazy.
And it's on days like that when I'm hyper and angry that I do things like scrape the car door on the side of the garage or rush off too fast without checking whether the car door is completely shut or the back door of the house is locked. I'm more likely to get into an angry argument with anyone who harasses me -- not just potentially dangerous people, but a bicyclist who zooms past me too fast on the sidewalk or a homeless man who screams at everyone.
None of this behavior is useful and it can be dangerous.
Being calm and centered is a key element in keeping yourself safe. It's easier to pay attention, to be flexible, to listen to your instincts when you're calm. And if you have to fight, you'll know it.
But it's not enough just to say to yourself "stay calm." You need to teach your body and mind what that really means. There are many ways to do this. You can learn it in martial arts training, particularly in an art like T'ai Chi where you learn long forms. You can learn it from yoga practice. Meditation training can also teach you to find your calm center. All of these practices are valuable ways to learn this very important skill.
You don't have to invest a lot of money in classes to learn this. I picked up some good basic meditation practice in a book by the Zen Buddhist master Thich Nhat Hanh. There are also meditation centers that offer basic training for small donations.
You don't have to commit to a Buddhist or other spiritual path to learn these skills, but you do need to practice.
Of course, holding onto that calm center in stressful times is difficult. It's one thing to find your center while sitting in meditation; another to have it when walking down a street at midnight. But the first step is figuring out what calm and centered really means.