People don't understand because, well... It does seem silly that we cannot merely calm ourselves down. I used to feel the same way when I saw people with anxiety and such... Until I had one of my own. And more, and my life has been chaotic ever since.
People, for the most part, will NOT understand unless they've experienced a panick attack. But you can try and explain it. When I sat my girlfriend (Now my fiancee) down and told her how these attacks made me feel, she seemed to understand a bit more. We had gone from a happy couple that'd frequent bars together and go out to just her going out and me sitting at home, too scared to even go out. She understood and I trusted her, but it sucked because we're both in our mid-20's and I want to ENJOY these years! But I knew that it was a work in progress and that eventually I'd reintegrate myself back into my old life, although probably with less drinking. But like I said, once I sat her down and looked deep into her eyes and said, "Look, this is what happens to me during these attacks just so you KNOW how it feels and I am not just being a pansy." Because, honestly, as a guy you're molded to believe that you're supposed to be made of steel. Emotions? NAH! I felt like I was weak, being controlled by such a small thing such as anxiety. But she understood and it actually brought us closer together that I opened up to her in such a way since that's what people in love should do.
Anyone that makes fun of you or isn't helpful isn't worth being in your life until they can be supportive. Negative energy is something that we do not need. Plus, I find that places such as this website are very helpful.
Best of luck to you.