Tips for anxiety attacks

I have been battling depression and anxiety since high school. I am now 31 years old. I've always been able to deal with it on my own but it is getting worse. I do have a dr appointment next month but I was just wondering if anyone has any tips to help calm down during an anxiety attack. I had an attack a few days ago and I had to lock myself in the bathroom with the lights off until I calmed down. Any tips would be appreciated.