> I also get nostalgic at times about the wonders of youth, experiencing things for the first time
Yeah, I guess at one point I'll feel like that too perhaps, but I still feel young, I feel like I have more energy each day than the previous one, and every month is experiencing new things for the first time, and personally I don't want that to stop and experiencing those things through the eyes of my children, I want to continue having those experiences myself, together with my wife :) I guess that's where the offhand "I'm selfish" sentiment from my previous comment comes from.
> If I do nothing else in my life, I would still feel immensely fulfilled.
Do you think you'd feel fulfilled if you didn't have children? Maybe this is the core differences, I feel fulfilled in my life already, more than ever and more every day, I live exactly the life I want today, and I wouldn't want to change it for anything. Even if I became deadly sick tomorrow, I'd feel fulfilled by the life I have lived.