Me too. We don't always get those choices. She was diagnosed with the aortic aneurism years back. The doc advised surgery. This would have her in rehab for a year. Close to 90 at the time she decided to just keep going, always with the specter that she could go at any moment rather than a year or more in rehab with no certainty that she'd be independent after. I think I'd choose the same.
I'll never be as sharp as her, my Mom was brilliant. But if you want to live like her start gardening, doing The Nation crossword puzzles to keep the body and brain sharp. Find causes you're passionate about and raise heck with your lefty friends. Maybe a demonstration every so often.
Other than that luck and genes I guess.