I do the same thing I do to avoid alien abduction. I don't worry about it. If either one does happen to me, I guess I'll be sorry I wasn't prepared, but I'm 42 years old and haven't had the need to hit anyone yet, so I'm betting it's not worth my time to worry about it.
I have started taking Tae Kwon Do, but self-defense never crossed my mind. I'm doing it because my 9-year-old is doing it and it's something to do with him, plus it feels REALLY good on my legs after riding.
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Work: the 8 hours that separates bike rides.