Jade, the heroine of Enter The Parrot, learns a martial art as part of her development. I'm a martial arts practitioner as well (though I'm not nearly as cool, nor a member of any secret societies, unfortunately).
So this is the page where I talk about martial arts and stuff like that.
I think learning self-defense is one of those great things that everybody should treat themselves to (along with eating well and having self-respect). Not only will you get into great shape and learn some cool moves (that look really cool on the dancefloor, btw), but you'll also learn useful skills and techniques that may get you out of trouble one day.
Think of it this way. If you're aware that someone can attack you, you're going to look at your surroundings in a different way. A lot of trouble can be avoided if you jsut take a bit of extra care. Like not taking the shortcut through the park at night. Or not hitching a ride with a stranger (or someone you've only just met).
When you see potential troublemakers up ahead, do you walk straight past them? Try to slink by unoticed? Cross the street? Your choices will mark you out as a potential victim, or as someone who might be more trouble than she's worth.
If you look at some of the choices Jade makes in Enter The Parrot , you can see what happens when you act too quickly - or fail to act.
What would you have done in her position?