Your mother's advice sounds terribly selfish, honestly. Our society is pretty much build on the fact that most people are in some way "good" and will not break laws and rules even if they could get away with it.

There are tons of stuff every day I could steal, knowing that any law I might break would not be enforceable simply because no one knew it was me. Littering in the forest. Dumping toxic materials into rivers.

All that works because most people don't do it, only a few.