So, I have had two heart attacks. After the first one, I started exercising more and working less, but there was concern that something might happen while I was fishing, walking, working, or doing almost anything ending in "ing." For a considerable time after the first heart attack I had pain in my left arm and upper chest, right in the heart area. Numerous stress tests showed no cardiac issues -- in retrospect it was probably medication-related or possibly muscle issues related to working out. But, I worried about it. I cut back on working started to exercise more and over a period of time the fear of "is it going to happen when I am out in the middle of nowhere" receded. Exercise helped the most for me: I felt physically stronger and in my mind it seemed if it happened again, then I had a better chance of surviving the second one.
It did happen again and I was in decent shape, eating well, working out regularly, a stress test a short-time before showed I was in excellent cardiac condition, but down I went again. After the surgeon was done with me he commented: "with your arteries, I will be seeing you again, next time for a bypass." Well, he is a surgeon. After that event, some of those initial feelings of vulnerability returned and I increased my workouts, then a friend asked if I was interested in cycling and in 2010 I started a few months after the second event.
it was slow at first and I have had a series of knee and other issues that have kept me off the bike, but my cardiac conditioning has improved significantly. Last year on more a less a whim, I tried climbing Haleakala on Maui because, well my wife and I were there and so was the mountain. Short story, I made it to 8000 feet, a couple thousand feet short of the top. In the last couple of hours of riding I started to beat myself up some with those thoughts of not being able to do it, etc.... And, at some point I just became glad I was there, glad I could do what I could and not sad about what I could not do. "Everybody gets knocked down" as the saying goes and it is getting up and going on that helps to keep going on.
That depression thing after a heart attack is real. I got past it with exercise and just getting on with things, but it was not an easy path. You can do it.