I got bullied in school a lot. In other words, I got beaten on for years. Coupled with years of goalie experience in hockey, I was eventually so used to stuff flying towards my face that I could take punches to my face without even blinking. When I eventually grew balls in 9th grade and fought back, I sent two guys to the hospital, one of them with broken teeth.
Only been in one 'fight' since then. I was in a store and window shopping while waiting for the buss, and some guy drops his smartphone on the ground, which I naturally step on, cracking its display. He flips out on me, threatening my life and what not. He eventually grabs my jacket and rips a seam, which pissed me off as I really like that jacket, and I knock him out. I don't even remember how I punched him, but he dropped like a sack of potatoes.
I don't have any martial arts training or anything like that, but I am pretty strong. I grew up doing sports, being as physically fit as a kid realistically get for a span of 10 years. I still have to work out occasionally, or I get so restless that I can't even sit still, and that drives me insane.
So yes, I'm probably capable of defending myself better than most, though I tend to avoid physical confrontations.