Learn how cardiac arteries are damaged by improper diet and exercise, lifestyle, and stress
, and time.
Make very bad food choices every meal, every day, and be highly stressed, and a person may make it happen at a youngish age. For the average person not trying to force it, a heart attack
does kill occasionally in the 30's, extremely rarely in the 20's.
With the right diet, exercise, lifestyle, etc, you should live well into your 90's or even to 100, and can be as healthy and as happy as you care to be until your last few months, possibly to the very end.
Don't worry, be happy. Eat well, be active. You can outlive them all if you like. Have friends, be a friend.