A powerful scripture that I think of often is Paul's words to the church at Philippi: "...work out your own salvation with fear and trembling." Perhaps if we truly do this...with fear and trembling...we will be less likely to stray from the narrow.
I still wonder though: Could your path be more narrow than mine, and yet be God's path? Else what is there to work out? Maybe, as you suggested, Scott, it is such small things as sleeve length, what constitutes jewelry, and which kinds of screens are holy.