Just keep breathing. That is what I tell myself when I start feeling anxious. When I still have time before the anxiety attack completely consumes me, I tell myself to just keep breathing. I remind myself to breath through the fear, that it won't kill me, despite how awful the feeling is. This is how I try to calm myself through an anxiety attack.
Anxiety is different for everyone. What may trigger an attack in one person may make another feel better after having one. The symptoms of an attack may be different depending on the person. For me, I get an upset stomach, I have trouble breathing, I feel the stress making my neck and shoulders tense up, and a lot of times, I just burst into tears. In the middle of an anxiety attack, it's difficult to stay calm. That's why it's called anxiety: it is the lack of calm.
For me, an attack can happen anywhere. I could be in class, and all of a sudden, feel like I can't breathe. Sometimes I feel like I'm about to pass out, and sometimes I can only feel the attack coming on and I try to fight it off. Regardless of this, it always leaves me feeling horrible.
Despite how logical of a person I am, the irrational fears take over my mind and I become all consumed by a fear that I can't explain. Everyone that doesn't understand what it's like to suffer from anxiety disorder just tells me to calm down, that everything is okay. In my mind, everything is not okay. My body is having a reaction to something not being okay. The worst thing someone can do when I have an anxiety attack is tell me to calm down.
I think that different things work for different people to relieve the symptoms of an anxiety attack. The best way for me to feel better is to just get a hug from someone I trust. This may not necessarily be the solution for everyone though. While a hug works for me, some people don't like physical contact when they're feeling anxious. I understand that feeling because even though a hug normally does the trick for me, I sometimes become so panicked that I don't want to be touched at all.
My point is that everyone is different when it comes to anxiety. It rips through you, making you feel like the world is about to end and there's nothing stopping it. It consumes you to the point of being unable to focus on things you care about, and it inhibits you from doing something that you want to do because the anxiety feels like it's too much. Long story short, anxiety is the most terrifying monster there is to someone that suffers through it. All I can do to keep in mind that I'll live through it, is to just keep breathing.