There's something I think people don't fully understand about anxiety. In fact, I think that unless you've battled it, it's near impossible to understand, because it's what happens inside of the brain when anxiety takes the reigns. And without anxiety, you don't experience it. That "it" is that when you battle anxiety, you can't not worry. And trying to not worry makes you feel worse. Because then, you start to worry about worrying. You end up chastising yourself for an illness you can't control. It doesn't matter what the topic is, or how trivial it may seem to others. It doesn't matter how unlikely it is that what you're anxious about will actually occur. And here's the piece that I think can be most frustrating to those we're close to, those who witness this anxiety: no amount of reassurance will make us feel otherwise. In fact, it often makes things worse.
Here's the thing: unless you are, somehow, the person who can actually make a situation OK, you're just guessing. You may think it will be OK. Or you may mean that even if the worst happens in a given scenario, eventually, the person will get back on their feet. Or that what they're worried won't be that bad. But you're looking at it from your perspective, not from what's going on inside their anxious mind. You can, in no way, guarantee that what happens inside their head will be OK. You cannot control how their anxiety or depression or panic acts. You can't insure that they won't feel like they can't breathe, like their brain is going to explore or their body break down. You probably can't control their external circumstances (unless your specific actions are what they're worried about in the first place and then hell, do something about it!), and you certainly can't control the internal ones. So really, you don't know that it's going to be OK - not from their perspective and experiences, anyway. And yet you promise it will be, and want us to believe you and act accordingly. You want us to control something in our brain that we cannot, simply because you tell us it will be OK.
Continually trying to insist it'll be OK only alienates us. It makes us feel like you don't understand us, or how we're experiencing the situation. It invalidates, in a way, our worry. Especially when you keep insisting on it, even when we tell you that we know the emotions we're in for, and they are not OK. Basically, you're telling us that you know our body and brain better than we do. That, without being inside of our head, you know how it will react. You may not mean it this way, but it's how it comes across to use nonetheless. In a way, I almost wish that you could have a glimpse of my worry - that you could spend even a second or two inside my head. If you understnad what the worry felt like, I wouldn't feel so isolated in my feelings, so wrong or broken for being worried.
Now, there may be times when you can help to control at least the external circumstances. If we're anxious about money because we're having trouble paying the bills and you offer to help, you actually can make the situation better. But most of the time, this isn't the case. There's rarely something you can do, right at this moment, to improve our worry. Partly, this is because much of our worry is about the future - I won't be able to do that, this will happen, that will occur. And because you can't control the future, you literally cannot prove to us that these things we are worried about are not a problem.
So what can you do to help? Stop making our worries feel trivial. Stop trying to convince us of things you have no actual proof of. Stop trying to pretend you know what will be going on inside our heads, which is where the anxiety lives. Be there with us. Listen to us without contradicting how we feel or think. Promise us that you will be there, whatever happens. Let us know that we aren't alone, that even if the worst happens (which surely we're anxious about), that we will at least be going through it together. That won't eliminate our anxiety, because it's an illness - and illnesses aren't cured with kind words. But at least it will let us know that you are there, and that you don't think our anxieties silly, and we are not so isolated, misunderstood, and alone.