My defining moment would have to be my mom's journey from symptoms to a diagnosis of Multiple Sclerosis when I was a freshman in high school. She had weird vision problems for a year or so which docs couldn't figure out, and I was really worried she would go blind or die. the diagnosis of MS was a relief in that it gave clarity and answered a lot of questions. she's had a pretty average course over the last 15 years, and now uses a wheelchair when she is out and a walker around the house, but is mentally sharp.
since this coincided with a time when I was trying to find my path to the future, it had a strong influence on my career choice and life in general. I was really interested in architecture until that point, but coupled with a low demand for domestic architechts and my strength in math and science, I decided to work on Ms research. I majored in biology in college, where I worked on an animal model of MS to understand what the immune system is reacting to, and then got a PhD in immunology, where I analyzed blood samples from MS patients and people with other demyelinating diseases to further explore the immune system. It was an eye opening and interesting 8 years. Now I've left the research track but still have a passion for MS and advances in diagnosis and treatment. I also started participating in MS bike rides every year since I was 16 (old enough to go alone at the time), and they are something I have kept doing and gotten DH and several of our friends to participate in. In fact, I'm plotting for how to manage riding while caring for a newborn this September, and hoping I have healed enough to get on a bike by then!
along those lines ... what did you want to be "when you grew up", and how did that bear out now that you are (theoretically) grown up?