Nobody wants to have bad things happen to them, especially if those bad things involve harm to their body.
Which you know, of course. That's obvious. But there are related implications that I find very reassuring and that really didn't occur to me for years. Once I realized what this truly meant, it became much easier to calm myself down in a variety of triggering situations.
You want to avoid catastrophes, and so does everyone else. So does our society in general. This is why so much of our world is designed to be easy to use for, let's say, those who don't have a lot of common sense or don't think things through. This is why you'll encounter warnings like don't drink this chemical, don't let your child play with this plastic bag, don't stop the chainsaw with your hands, etc.
Not only do we get these warning labels for almost any imaginable danger, we also have more common warnings drilled into our head by the people around us, pretty much from childhood. Don't go swimming during a storm. Don't get in a stranger's car. Everyone learns the general scenarios that could lead to danger, and, depending on their personality, respond with varying levels of caution.
Which brings me to you, unfortunate person with severe anxiety. I am guessing you're extra cautious when confronted with any of those scenarios or warning labels. I am guessing you also have a wide range of scenarios you have decided are dangerous all on your own, without anyone else telling you so (or agreeing with you) and are constantly doing your best to avoid those scenarios or take (most likely unnecessary) steps to make yourself safer.
But remember, nobody wants to have bad things happen to them. Especially if those bad things involve harm to their body. And with regards to whatever you fear, ask yourself: if there was an actual danger of this behavior or situation causing harm to my body, wouldn't I have heard about it before? Wouldn't I have heard or read something, somewhere, about it potentially causing harm?
If eating parts of the apple too close to the stem could cause me to get sick, wouldn't I have heard about that?
If this dental procedure I'm about to go through was likely to make me vomit, wouldn't I have been told that was a possibility?
If watery sour cream or watery yogurt was a sign that it was likely to be bad in some way and give me food poisoning, wouldn't that be one of those things that I was warned about all my life?
Those are just a few of my own personal examples.
I don't know how to stop these little worrying thoughts from popping into my head, as they still do, regularly. But I have found this line of thinking to be an effective countermeasure, a way that I'm often able to dismiss the worry.
If anything has a good chance of making you get sick, it's incredibly unlikely you wouldn't 1) already know about it or 2) be warned beforehand.