This is all very intersting!
I always thought he meant that if you know where your wife, your gun and your horse are, then you won't find yourself in unexpected trouble. BUt if any of those things fall into the hands of someone who makes a bad decision, then you can be held accountable for NOT keeping better tabs on what is yours to care for, and what was most valuable to you.
I think too some of it was based, maybe just vaguely, on the fact that as a child, my dad starved, and when he had a good horse to go hunting on, and a good gun to shoot something, (later a good wife to cook and make a home for him) that you better keep the things that truly matter close to your heart and they are not ever to be casually loaned out. That the difference between being homeless and hungry or not could be summed up with a horse, a gun and a wife.