Here is a link to an interesting short article by Chris Fry about knife carry for personal defense. It's from PDN, so I thought that I would post a link to it.
We all carry knives for different reasons, one of which can be personal protection. Even if you don't get professional training, it's a good idea to think about protecting yourself and your family with your knife or whatever you can. You can visualize situations that could happen and think about how you would react. You can practice drawing your knife, manipulating it into position to defend yourself and how you would use it. Michael Janich has some great training video's at the MBC website that can be a start to protecting yourself and your family.
You never know when something bad can happen and being prepared
is always your best defense.