Funny, I've always just assumed that I'd live to be 100. There's no family history to support that; it's just what's always been in my mind. Apparently, I'm not alone. FWIW, I just read in Thinking, Fast and Slow by Daniel Kahneman
that most people think they will live longer than average.
Congrats for changing your lifestyle to change your odds for longevity.
[For those with rusty Latin, "Seize the day, trusting as little as possible in tomorrow." - Horace]