Good post anon (and so was the pb post).
I've been thinking about this for 10-15 minutes and I could write a life story…
but I think courage is to some degree learned, and that seems to be reflected in your story and in my own experience.
I had never perceived myself as particularly courageous, although I had increasingly come to think of it as important when I was very quickly confronted with a situation where I had promised to assist a stranger, and then others suddenly confronted me with a gun. I thought of fealing sorry for myself, but realized I had but a moment to seize the gun, and it hit my that I didn't want to die like that, so I did. And I got it and got away with the gun, and everyone lived to tell the story (and the perps got time, sort of).
But then a year later I was suddenly confronted with a friend threatening suicide via large knife and I had only a moment to realize that (for complex reasons) I had to act immediately or pass the buck. I was able to get her to give me the knife, but only by placing myself in a position where she could have stabbed me.
Both of these events fed into subsequent events (years later) that led me to realize I had to commit myself to this particular endeavor.