Ah what a lovely and amazing event in your life. Your recall is so vivid. Maybe around age 18 too I used to wonder about Heaven and Hell, although my family were "Christians" did not go to church, but my brother and I "Sunday school" ... also in UK "schools then religious instruction" was one lesson per week, and Assembly and a Hymn every morning and The Lord's Prayer. I did not understand why but the Jewish children sat outside in the hallway every morning.
I suppose I started wondering with my own family, my Grandmother lived with us.... her husband dying leaving her with four young children. As she was ageing I wondered if and when she died and went to Heaven, would she again meet her beloved husband and would she be as she was , in her 20s when she died, or as she would be - in her 80s when she died - and had he remained "young."
I then met relatives in Canada and and old distant relative and her second husband and as just young myself again wondered if when she died would she go to Heaven and would she meet both her husbands there? Over the years the visions of Heaven with Angels, and Hell with fire and the Devil, have faded... yet when I was diagnosed with cancer and given 40 per cent chance of living five yeas (in 1985) I had a strong feeling that should I die soon, my "spirit" would go to, or return, to a sphere ... to a "creator" or to the beginning of our Universe and that I would again be joined with my Dad .. too long a chat to continue but I suppose for each of us we have personal feelings of what might happen ; I am not afraid of dying, my children are adults, I have had many ups and downs in my life but am satisfied with it although I made a lot of wrong choices. But I am afraid of suffering..... as my mother did for ten years before her death, as my ex did for several years before his and of course many other human beings in many countries of the world from babies to the aged.
As they say: there is only one way to find out! Or we may be like trees and plants, have a life expectancy and when it is over sooner or later, become part of our Earth.
Whatever everyone believes, I hope that for ALL humans there is at the very end "Peace"