Okay, I do have to interject here.

99.9% of the time, it would be paranoia and you were just too high.
0.1% of the time, maybe you DID have something happen to you. I blew a blood vessel once while high. Maybe it was coincidence, maybe not. But there is still the chance someone could have a cardiovascular event while high, whether it was related to the drug or not. So don't write it off completely as a panic attack. Because shit does happen, it's vanishingly rare, but it does. It happened to me.