I'm probably in the minority here but I often think about preventative care like exercise and eating healthy now as insurance against a future where I'd be stuck in a nursing home in my final years.
We would all like to think that "the end" would come at a ripe old age with a peaceful death in one's sleep. Sadly that's not usually the case. People who live a long time can expect a cascade of long-lasting chronic health problems leading to their death.
If you're going to focus on diet and exercise do it for your quality of life NOW and not for the distant, unpredictable future.
There's something to be said for dropping dead at around 80 of a massive heart attack.
Personally, dying at 70 seems about ideal to me. Of course maybe I'll change my mind if/once I reach 70.
My dad is in his seventies, and just built an addition on the house alone, by hand in his free time while working a full-time job. From pouring the slab, to framing, to roofing, to electrical just because he was bored.
I think there's a lot to be said for arriving at your seventies still being the kind of person who goes, 'I'm bored, I need to go and build something with my hands.' There's obviously a lot of luck involved in not having any major health complications, but fortune favors the prepared.
Being relentlessly active and curious is a really, really big deal as you age and it's so easy to fall in the trap of retiring, and sitting on the couch with a beer watching Fox news.