Here's a fellow "almost 80" -- with a life that has gone thru three cycles of hard and 'not hard' financially. I still am able to live independently -- with a senior cat who gives me lot more than take (seeing it curled up close by on waking up even as one shoulder has become crooked I keep him as much active by letting jump down from the kitchen and bathroom counter tops multiple times before giving food. Or do rough play that engages his most body, risking bites (yesterday I got two, one bled a while, but it was labor-of-loving play)
But I find this year I am not as strong in some ways (I can't do full pull-up from a tree branch in my neighborhood park) but in some other ways (walked up the stairs with 15+ pounds of groceries all 13 floors, testing my heartbeat when it peaked at more than twice (about 140 per minute 5 floors from top.
So far no meds, no surgeries, no seeing my doctor for years. I'd some chest pain; tried to expand my rib-cage but didn't seem to help, went for a brisk 45 min walk on uneven surfaces when possible and right now as I write these lines I feel strong and alert. But what truly helps me I believe that I get up each day with the work that I believe I must accomplish, the so-called having a purpose. Prof Patrick Hill of Washington Univ at St Louis has done much research and believes it's the central cause that helps us live with fewer issues, no matter what stage. Social Contact is crucial in his msg. And that is something NOT in my control, and it keeps me looking for ways where to find a few of those with whom I'll have an invigorating time together. Seniors seem to be second most lonely (first are 14 to 20s)
I wish you luck with your health and fitness.