Mentally I can take care of money, manage the bus system, get to and fro on time, and stand in long lines and walk miles at Rome’s Fiumicino International Airport (where no one takes their shoes off). To travel solo internationally you must be able to manage an airport from start to finish.
Physically I have incredible stamina. It’s a gene thing. I had practice throughout my childhood as I worked hard to keep up with my grandmother as we walked down 5th Avenue in NYC. She set off at a vicious pace, and I notice I am keeping up the tradition. My mom, who lived to be 101, took a daily walk up until the last nine months of her life.
Yesterday, according to my phone app, I walked 7 miles, took 17,959 steps, and climbed the equivalent of 33 floors. This was my Duomo climbing day, thus the 33 floors; but the miles and steps are pretty accurate for all my solo travel days.