In some ways I can relate-i am 32 yr old woman and had a tia (stroke) I thought I was healthy,young, and slim...It is going to go on five months but the first two and half were hell. I couldn't sleep and constantly thought I would die that night. Even when all my blood work came back great I was not convinced.
I recently joined a group that discuss fears as heart attack, stroke, cancer (ask his doctor if they have one of these in your hospital) when you are confronted with death it is one scary thing-especially so young.
It will take time-i am now relaxing way more and I recently decided to do a walk-a-thon for stroke awareness. When the smoke settles do something positive so others can be aware of the danger of heart attacks.
I still get nervous if I wake up in the middle of the night but I calm my self and say "everything will work out." I usually fall right back to sleep
good luck