Hi there and welcome to the site. I am also (close to) 50 and on Trikafta. Stamina and resilience are definitely tough to come by given all of our obstacles, but still very achievable. When I prepared for the NYC Marathon, stamina was my main focus during that training period. For me, consistency and having a game plan (written down in my journal) were my keys to finishing. Each week (Sunday night worked best for me), I wrote a training plan for each day for the coming week. Then I really aimed to hit each day's goal. For example, my week's goal may have been to cover 15 miles. So, each day I wanted to run 3 miles. Of course there were set backs and things that came up as life has a way of doing - but then consistency comes in. The more consistent I was at trying to reach my daily goal, the better it became. If I missed a day, I wasn't happy, but I also learned to let it go. This is the mindset that I found worked well. So I would say, my tip is to pick a goal....whether it's a particular hike or even a marathon (hey, why not?!) and then break it down into smaller, more achievable and managable daily goals. Each week check in with yourself to see how you're trending. Maybe you see a pattern develop? Address any obstacles ideally before they get in your way. For example if you know today that a saturday workout isn't possible, work that into your plan now. You will be surprised how much consistency is improved by just doing that. I hope this helps a little and I wish you the best of luck!!