Is My Journey Into Fitness Turning Into Self-Defense?

Karate is my planned route back to fitness and every journey starts with a single step. Two classes survived, pain moderate and enthusiasm maintained. A good outcome by my standards. Although, I admit, they are standards set quite low. I am hoping that the key to my fitness success, is continued slow progress, rather then a quick burst of activity that cannot be sustained. Session two involved "sparring" or fighting. As a stranger to the class and martial arts in general, I was the only person in the room (dojo) who found the concept of hitting another person odd. For now, I stand by this point of view. However, it was a requirement of the class that I got over it and get going. Reassured by the instructor, who stated clearly for my benefit, that a white belt was not a true opponent, but rather someone to be instructed, I got going. First, I was paired with a a nice boy of around 11 years of age with a green belt, who kindly showed me a few block-strike combinations. Obviously, neither of us hit each other, but it made sense and I could see how it would work, as long as your opponent remained stationary. Next up, an adult brown belt. He had finger strapping visible under his protective mitts and suggested that I get over my fear of hitting him, by hitting him. I suspect that it was this approach that resulted in his hand injury. I did hit him, since it was obvious that I couldn't do anything, short of producing a gun, that would actually injure him and also, under the rules issued by the instructor, he couldn't hit back. Despite this, hitting him didn't feel good or release any stress, but I did realize something; my fear of hurting other people is equal to my fear of being hurt - at least in the absence of real threat. This is odd, since it must be a basic instinct to protect yourself and the people close to you. Is it just a gender thing? I, like most women, have grow up with little direct experience of violence and the assumption that violence is a mans job, in circumstances of last resort. What a nice world, but what if my world gets less nice? Now the gender issue can't be the whole story, but if it's part of my reticence, aren't I leaving myself open to any would-be attacker? When I say that I have not experienced violence, I do not mean that I haven't been assaulted. There were a handful of occasions when I was younger and went out more, that I would be groped, followed or verbally threatened. Most were frightening, one required a sharp get-away, but none actually resulted in harm. I suspect many women have experienced similar scenarios. Clearly, these outcomes were chance and I could have quite a different and unpleasant story to reveal today, if I had not been so lucky. Although I don't feel threatened in my everyday life, my answer to the question, "would you be prepared to hurt someone who attacks you?", is "yes, absolutely". Surprisingly, this class has revealed not only my physical inability to do this, but also my mental inability too. So, regardless of any fitness drive, I need also to change my mental attitude.