Widows & Widowers Support Group
This community is dedicated to those who have lost a husband, wife, or partner. Anything is open for discussion here, with the hope that we can focus on grief, bereavement, life after loss, and continuing on after a great loss.

Is your friend willing to talk to someone about his fears? It sounds like they are starting to take a toll on him, and that in itself is the antithesis of self-care. I hope he would be inclined to talk to a professional.
Just my 2 cents.
That's just my two cents worth added in, too, for whatever it's worth....
I still wake up sometimes in the middle of the night in a panic, thinking I'm going to die. It takes awhile to talk myself back to calm again. My husband Cliff died of a heart attack in our bed - he woke up gasping for air and that's how I woke up, to find him gasping and he died in my arms. So I am well aware of where my panic comes from - what started it. It doesn't make it any nicer to deal with, but it helps to know some steps to deal with it. CBT would help him.
I think your friend should see his doctor, get the full check-up to put his mind at rest, and get a referral for some CBT so he will know how to handle it himself. Life is meant to be lived, not just endured, nor stressed over our mortality. He doesn't sound like he is able to enjoy his life.
Hope this helps.
Love and Hugs,
Martha