Coming to terms emotionally with what you know intellectually (none of us will live for ever and most of us have no idea when our time will end) is hard, whatever the reason for that sudden epiphany! I am not sure it's any easier for the older than it is for the younger. Irrespective of faith, we are hard wired to avoid death and it scares us accordingly. But I am pretty sure it is a good thing when you do come to terms with it and acknowledging the fear is the first step. It's not morbid and it often makes your appreciation of the rest of your life all the better. There are precious few 'benefits' of having cancer but reducing that fear has been one for me.