Phobia's and their resulting panic attacks

I often reflect back to the surgeries I've had in my life. Six so far. With every one of them there is one common factor. When it came time for me to get the prep shot before the surgery I would experience an extreme panic attack. Even a day before the shot I was subjected to extreme anxiety, putting myself through self torture anticipating the coming shot. As a teenager I even tried writing notes to myself, telling myself to be strong and just take the shot. It never helped. Every time the nurse would come in with that needle, It would take three sometimes four or more people to hold me down to give me that shot. Yet all of my life I've noticed I have a very high tolerance for pain. It was never the pain that was the issue, it was a phobia of needles, of that piece of metal being stabbed into my body. I still suffer from this phobia along with others to this day. My son and daughter still have their phobia's of running water. My son will go into a panic attack if a small scratch produces a little blood on his skin. Where do these phobia's come from? Why with the autistic do they produce these meltdowns of an extreme nature. Again to me the only answer I can see is the fear itself. Our emotions are too high strung. I have no memories of a single shot causing me such harm that I was traumatized by it. Running water has never harmed my children. How can we learn to handle these fears better, to turn down the volume on our emotional amplifiers to a normal human level. Unfortunately I don't have the answer. The only thing that I can do now is warn nurses and doctors ahead of time that I WILL experience a panic attack which IS a result of my anxiety of needles. Maybe this is what we have to do with our children. Accept what is going to happen and just explain to the world why. If they don't understand, there's nothing we can do. Fear.......what can we do to conquer it? Will it ever go away?