Indeed, there was an event (actually two, but this is the more significant of the events), albeit it was not for the better.
When I was a child up until my early teens, I knew what I wanted to be when I grew up. I wanted to be a doctor, and later on more specifically a dentist. I had mapped out my future to an extent, and my good grades morphed into excellent grades in high school, reinforcing my decision.
When I was fourteen, my grandfather was admitted to the hospital for surgery on his lungs. He turned out fine, of course, but I realized that I didn't want to be a doctor of any kind. I had wanted to be in medicine because it was a way to make money while helping people hands on. I also liked the complexity of human biological systems, as well as the idea of repairing broken systems.
But when I visited my grandfather in the hospital and I saw all the people who were sick, it hit me at that moment that I could never be a doctor. Believe me, I wanted to help the people, at least in my heart, but in the physical world the idea of actually getting physically and emotionally involved with patients -- even in the all too cursory way that doctors sometimes deal with their patients -- repulsed me. I didn't love people enough to put up with bodily fluids, to do all I could to relieve their pain, or to even give them reassurance or advice. I realized that it was not for me.
Ever since then I've struggled with what I want to be, even to this day. It's in part why my life has been so aimless. I want to help people, but without...you know...touching them.