...don't let your left hand know what your right hand is doing...

Notice that the angel is standing on Homer's right shoulder while the devil is standing on his left (aka, sinister) shoulder

A thought that occurred to me is that this Bible quote (Matt 6:3,4 which is part of the Sermon on the Mount) had a secondary meaning to the Jewish people who heard it.

But when you give alms, do not let your left hand know what your right is doing, so that your almsgiving may be secret. And your Father who sees in secret will repay you. 

The right hand was the clean hand and the left hand was used for unclean purposes, i.e. wiping one's bottom.

For example, our better self might take meals to an elderly shut-in. The secondary message is to not let our sinister side take advantage of those shut-ins by asking for valuable knick-knacks or offering them ludicrously low prices for them.

Or, we might offer aid to a widow out of the goodness of our hearts. Our sinister side might start murmuring that we are entitled to fringe benefits.

The best way to avoid that temptation is to quickly forget that you did those good deeds. And the best way to do that is to give the credit, the glory if you prefer, to the Holy Spirit. All we can take credit for is that we listened.