Word man I know what your going through.I used to get them FREQUENTLY like as soon as I smoked my heart would go out of control because I was expecting it.Its mainly a mental thing.You just have to chill, try to have a good time, get up and walk around and pace, breath deep breaths and chill, think of things that will put you in a good mood, like going to the movies that friday or hanging with some friends that night.YOU JUST GOT TO CHILL, I swear you'll feel better.Keep telling yourself its mental and it will pass.I havn't had one in awhile, well I did this saturday because I had unbelievable cotton mouth and we were walking.But I over came it.Just chill and try doing the things I said.A cup of water or some food will help take your mind off of it.