Thanks Freebase
For me, it wasn't so much using rationality. I think that to your mind and body, becoming worried or scared in situations that have scared you before isn't necessarily irrational because even if the situation is harmless, you do have unpleasant experiences with it from before. I know some people are scared of spiders. If I had had a spider problem then, I think I would've been scared of getting scared when I met a spider if you know what I mean.
What helped was refusing to let fear control me so I would choose to do things, knowing very well that they would cause anxiety. Often, it would go better than I feared and even if it didn't, at least
I was deciding what to do, not my fears. I externalized it in a way and refused to listen to it. It gave me back the control that the anxiety had stolen away from me. It took some time, but not long after I had actively started fighting it, I won just about every battle I had with my fears.
The change and the realization I could beat it didn't just happen out of the blue, though. For a long time, it was such a common feature in my life to be fearful, but then one day I was super excited about this IRC bot I was compiling and setting up .. nerdy, I know
Still, later that day, I realized I had been so absorbed in what I was doing that I had forgotten about my anxiety. I had pretty much had a normal day! From then on, I knew that it was possible to have a life without fear, so I mentally grabbed a hold of the problem and actively decided to do something. I told my parents and even my teacher about how I felt which helped quite a bit and then I started battling it on my own. I went to a psychologist once and he said I was already well in a recovering stage where I would come out of it on top, so he didn't think I would need more counselling then.
He was right
I think once you figure out the right way to battle it, there's only one way I think which is forward.