I suggest you read the guidelines for Graves’ thAt on the main webpage of this site. i can pretty much tell you that you can’t really prevent it. But if you do have Graves’, with treatment, which can take a while, you will feel much better.
It certainly can be dangerous if left untreated. It is like trying to drive 80mph in first gear. Many people with untreated Graves’, right at diagnosis, have dangerous heart rates of 120 or more. Too much circulating thyroid hormone is not good.
As Kimberly says, it would be helpful to know more of you situation.
In the meantime, you have found a good and reliable website, and you will learn that you are not alone!
Shirley