I don't know if this will help.

But the heart racing thing I have been in the same EXACT boat as you in that one.I remember I smoked a joint before school with 2 friends and went to class my freshman year, never in my life to experiance paranoia.Well this day in class was a little different, I could hear my heart beating extra strange right in my head and it would go fast and fast and fast and I would think "Oh Fuck its going to stop! I'm going to have a heart attack for sure!" Then visions of me freaking out having a panic attack and flopping on the ground while my teacher goes ape shit and gets the nurse start started to race through my mind.Well I put my head down and I really don't remember what happened.I just know eventually the high went away and so did the paranoia.Well after that I was a marked man, never to smoke weed like that again, I found I thought my tolerance was so low that if I took one or two hits I was set..Not really it was just me being a pussy because I kept thinking I was going to die if I smoked to much weed, and none of my friends understood.Well after research on the drug to see what was really happening I just realize it was paranoia attacks which were normal.

This is what always cures my attacks when they come around, even htough they don't that much anymore.JUST tell yourself NOONE has ever died, or "OD'ed" off smoking weed.It would just be a very delusive, abberrant thing if you did.Just really dosn't happen.Then think of something that you can look forward too that will make you happy, like hanging out with friends later, going out to eat, watching a movie, going to a show.AND JUST chill.And try not to do your rituals there just there to make you freak out more.