One thing that I say is that "I can do anything" as I say this I touch my fingers with my thumb. It calms me down. I do it over and over until I start to believe it myself.

As for the cycle, I believe it is stress. I've heard of some being two weeks long. Don't worry it will end. I'm not a doctor but I do know stress will do funny things to the body so just take some time to relax