Please, please don't use a knife for self-defense. I realize you've been in Jiu-Jitsu for 10 years, but there's a reason why many of the most-respected self-defense instructors in the world advise people to never use a knife in self-defense. I've got about the same amount of years experience in martial arts as you (TKD, and I've taken numerous self-defense courses involving weapons with neighbouring clubs) and never in my life would I use my knife in a fight.

At best you win and get charged with assault with a deadly weapon and face prison time even if you had good reason to defend yourself.

At worst you lose the fight because the other guy feared for his life once the knife was drawn and decided taking your life was necessary.

In fact the last time I did get in a fight (no choice, unfortunately) I pulled out my knife, tossed it and we fought in a (relatively) civilized manner. We shook hands afterwards and the other guy mentioned that he had a knife too and was about prepared to murder me had I not tossed my knife (turns out he was an ex-con and didn't use his knife because he didn't want to go back). Before that fight I was still on the fence about whether or not knives are a good self-defense weapon but after that I completely changed my view.

I know my suggestion is a huge longshot, but for your sake I really hope you consider not using a knife for self-defense... It raises the ante in a street fight and when the other person believes his/her life is on the line, they'll use anything as an equalizer-- knives, pipes, tools, you name it.

Anyway, sorry for getting so preachy. I had a friend in high school who died after someone broke into his house. This guy was an exceptionally-good fighter, but apparently he pulled a kitchen knife on the intruder and during the scuffle the guy managed to get ahold of it. Stabbed in the neck, and found hours later by his own grandmother. (They caught the kid who stabbed him, if you were wondering.)