I think most of us would do the right thing most of the time if we were sure what it was. (Heady discussion at lunch today about the pros and cons of fundamentalist religion: it does give a secure sense of right and wrong about many things.)
But would any religious code tell me whether to keep working at the moment or take a nap or the afternoon off and start again refreshed? Maybe it's too small a matter to matter. But such decisions often feel quite important to me. ( See obsessive compulsive disorder: scrupulosity)
Once I righteously kept working (which involved driving to a copy center) when I was very tired. I got hit by an 18-wheeler and my car was totaled. It was half my fault; I thought he was signalling to me to drive out in front of him, but he wasn't. Would have been better if I'd taken a nap. But how was I to know?
A person could waste a lot of time and energy and joy trying to make the right decision about everything.