It reminds us that when Moses was away on the mountain, the trumpet was sounded in the camp to warn the Israelites not to misconduct themselves.
For the Israelites of a later generation, blowing the shofar is a reminder that the Days of Awe are on the way and we should guard ourselves against spiritual or ethical lapses. Whatever we can do to enhance our religious life should be undertaken at this season, especially in terms of our personal Achilles heel.
Who was Achilles? In Greek folklore, a fabled hero whose mother plunged him into the river Styx and made his body invulnerable, Superman-like, except for the heel with which she held him. Eventually he met his death by being wounded in the heel.
In our case we probably all have an Achilles heel which needs to be watched carefully, though we are more fortunate than the mythological Achilles of ancient times since we can make a conscious decision to remove our problem.
If as often happens our Achilles heel is our mouth (a religious version of foot-and-mouth disease), we can get to work on Sh’mirat HaLashon, “guarding our tongue from evil and our lips from speaking guile”, as the final meditation of the Amidah puts it.
The tongue is such a powerful instrument that we can decide to use it only to speak positively and constructively and otherwise not to speak at all.