Up until last year I did most of my riding alone. T is fine with or without other horses around. Since her diminishing eyesight, I really haven't taken her out alone much. I think it's mostly me, not her, but I am concerned with the "what could happen ifs" because of the lack of sight.
With that said, I ride with a bell to alert other animals we're coming through and any hunters nearby. I have had someone tell me that they could hear that little ring-a-ling way before they knew what it was!
I always carry trail grooming tools (nippers, collapsible saw, surveyors tape) and a halter and lead rope. Can't get cell phone reception where I ride, but I let someone know where I'll be and approximately when I'll be back.
I'd like to carry a side arm because of the cougar sightings and the black bear in the area, but haven't done that yet. That's to be used only after
my horse dumps me and takes off so I can defend myself.
Of course that's going to work only if I'm not knocked out or very badly hurt! Yes, these are some of my "what could happen ifs)!
Oh, and I always wear a helmet. Am also considering a protective vest. My bones aren't 30 anymore.