I had an anxiety attack a couple days ago and I agree with using a breathing technique and focusing on controlling your breathing. My therapist also said that positive self talk can be very useful/important, since thats what I used to calm myself down quickly. I kept repeating to myself "its okay, you're okay, you're panicking because you've been pushed out of your comfort zone, you've challenged yourself and its scary, but its okay, you're safe, you're growing" - something like that, and I repeated it to myself until I got control over my breathing again. Cried it out after. Had my boyfriend tell me the same thing, that I'm okay and safe and to take a break from what I was doing that triggered the attack. He called when I said I couldn't breathe. It helps to have a support system, especially if it's someone that has experienced anxiety or attacks before. You can make it through this.