You are not an old fart until you are farting dust
Gotta love that quote!!!
You are as young as you feel, when I was starting my 50th year just past 49 I was bench pressing a max of 315# and a working weight of 275# 10 reps and for an old fart was doing way more than all the young bucks at the gym half my age.
Five years later I am falling apart, had gall bladder removed then two bouts of DVT in my left calf, I have not given in yet just getting warmed up, I plan to reach 100-110, so I must be just middle aged! You have nothing to prove and are competeing with no one but yourself. Get on with your trip and for good measure here is a quote from Mark Twain:
"Twenty years from now you will be more disappointed by the things you didn't do than the ones you did do...
So throw off the bowlines. Sail away from safe harbor. Catch the trade winds in your sails. Explore Dream Discover.