I'm afraid to die, so much so, the anxiety keeps me up at night. What should I do?

Lately, this fear has seemed to cause a resurgence of panic attacks, similar to the ones I used to have when I was much younger. I thought this was all over, but last summer I was partying, a lot, and stressing about university. All this seemed to stir something up and bring it all back. I don't know what to do anymore.