Wow, I could have written parts of your comments. I am 63. The realization comes in increments, doesn’t it? I tried something different yesterday. I walked a 1.5 mile easy trail but I used two trekking poles. And a friend joined me, which distracted me. I had to sit down once, and my face and hair were drenched with sweat ( another SFN symptom). But I made it! I can’t say it was pleasant, but I would much rather be outside than swimming laps indoors, which is my only other form of exercise now. The trekking poles helped tremendously.