I was never a particularly anxious flier, but did get nervous on occasion, especially with unexpected aircraft movements. The thing that completely changed this for me and made me much more comfortable when flying commercially was to learn how to fly a small GA aircraft. Once you spend some time actually controlling a small aircraft and getting bounced around by things like thermal updrafts and feeling how the plane responds (it wants to fly) and attempting crosswind landings and such gives you a lot more confidence and had a dramatic effect on how I felt about flying commercially.