Why does my anxiety seem to cycle?

I have off and on had problems with elevated anxiety over things I can't control (meteors, skyscraper collapses, unrealistic suspicions about people close to me). I am good at talking myself out of them, but they still happen occasionally, and seem to happen in clusters--like I'm fine for 6 months, and then I go through 2 months of much more frequent episodes. When I feel anxious I get nauseous and my hands and feet get cold. I recognize it for what it is, which helps me not overreact or exhibit odd behaviors, but it's still annoying to feel that way about such random crap.
I'm reasonably well-educated, healthy, exercise well and consume a healthy, balanced diet. What's the deal? Why the cycles, and what can I do to eliminate them entirely? You'd think if I had a bona fide disorder it would manifest more consistently...Any logical, medical, or well-backed advice would be greatly appreciated. Thanks!

I don't know the answer to that question. But it's interesting, it happens to me too. It comes and goes. And sometimes my fears of certain things go away and a fear of something else takes its place. Go figure.

You have not done much to completely cure your illness. Have you tried meditation? Read this:

That is very normal with mental disorders. A lot of them tend to cycle like that. That is one of the reasons they go undiagnosed so easily because symptoms come and go and even change. It is fundamental that you understand your condition and more importantly recognize the symptoms. Diet and exercise are a great help. Anxiety disorders are very hard to deal with because they are more of a personality disorder then a biological disorder. It would be great if you got involved in a support group or visited a therapist so that you can talk about your experiences. It is a great deal of help if you can remember when you experience anxiety that you are not alone in this world when it comes to anxiety. If you can frequently talk about your experiences and how to better handle situations it will make you more prepared and better able to take control of your life. You can learn to control your life, but they will never go away. Good luck.