I am ok with an edge to my left but not to my right. No idea why, since the only time I've fallen off a trail was when it was to my left.

It helps me to ride something like that if I'm following someoneby 50-100 feet - I watch them, and the trail behind them, and don't think about the edge. Probably just helps me focus ahead but I always do better with a "carrot" to make me forget the trail itself.