I usually ride alone. Even if I haul out with someone, I usually go my own way. My mare is super safe. She never bucks or rears or bolts or anything like that. I carry my cell phone in a holster on my belt and make sure someone knows where I am and when I'll be back. I usually call home once or twice during long rides to give them an update. I try to stick to high-traffic trails and avoid going across risky areas or go down trails where I might get lost. Oh, and I have an ID tag on my horse with my cell and home numbers, plus our home address.
Honestly, I don't think my horse could get rid of me if she tried, and so the only reasons I can think of that would separate me from her, would be if I was shot off her or we fell down a cliff. :P