If I knew 100%, I would not have had children, I would not have gone to college and I would have likely spent my short years here going from place to place, hiking the AT, hitchhiking to festivals, meeting people, and never settling down. It may sound bad to say I wouldn't have had children but if our reality was only 40 years I would never have gotten to a point where I could justify bringing them into this world. 40 years is not enough. No where near enough. If I was to die at 40 my youngest child would only be 12.
If I knew from childhood my life would end by 40 I would have just been a drifter.