Every medal has its reverse
or worthy conduct. It often has a front with a king or other top person's head to give it authority. The reverse side is usually plainer, and is not seen when it is worn at parades and grand occasions.
This saying suggests that the wearers of medals might not be quite as virtuous as the decoration implies. We all have our good days and bad days, and on a good day we might have been worthy of the award; but do we always live up to it?
It is very hard for an average human to be good, noble, and chivalrous all day, every day. We have to try to keep our sunny sides up, put our best foot forward and keep right on to the end of the road despite the off days when we fall from grace.