Can Experiences Truly Shape Our Lives?

Ever since I can remember, my one irreplaceable dream has been to become a physician. Never once have I gone through multiple phases of "what I want to be when I grow up" as many other children and adolescents have. Although, it has not been until recently that I took the time to truly ask myself WHY this has been the case my entire life.
I have come to the conclusion that experiences in one's life greatly impacts his or her future choices. Some people may have tragic stories to tell, and others joyous, but ultimately all have contributed to the life choices a person makes all through adulthood. I personally have come from a family in which diseases such as Diabetes, obesity, and cardiovascular issues are extremely prevalent. Most of my extended family has already been diagnosed as a diabetic or are considered to be "borderline" diabetics, and the leading cause of death in my family is heart failure. Living on the border, such diseases are extremely common so I have become very informed about health problems at a much younger age than many of my counterparts. While hearing of loved ones who had become ill with any of the previously mentioned health issues became normal to me, it wasn't until my younger sister was born that my entire world was turned upside down.
My sister, Monica, was born healthy with no seeming illness in sight. Unfortunately, after her first birthday she came down with Meningitis and Encephalitis. I remember feeling so helpless and wishing that I could do something to cure her. She was in the hospital for six months, in and out of comas, during which endless amounts of doctors told my mother that it would be a miracle if she survived. The doctors warned us that IF she were to come out of it, she would be deaf, blind, or in a permanent vegetative state. We refused to believe this.  I would go to the hospital everyday speaking to her and believing that she could hear me. One day right before Christmas, she woke up from a coma and we were allowed to take her home for the holidays. During this time, I made it my mission to "cure" her. She came home completely paralyzed on the entire left side of her body, so everyday I played with her in order to get her to try to move her muscles and hopefully get better. All of our praying, and hard work paid off because from then on she slowly regained complete function in her left side and has now grown to be taller than me, completely healthy! She is known in my hometown as "the miracle baby" because no doctor had seen anyone come out of an illness as severe as the ones she had. I truly believe this experience is what led me on the path I am today, motivated to become a physician. If I was able to "cure" her, or so I believed as a child, I will stop at nothing to do whatever I can to cure others who are ill. I truly believe this is my life calling. Do you believe you have a life calling? In your opinion, do experiences shape the long term decisions you make for yourself?