What is the meaning of [A miss is as good as a mile]

A narrow miss is as bad as a wide miss – they are both misses.

This proverbial saying dates from the 18th century. The first example of it that I can find in print is from the USA, in the journal The American Museum, Volume 3, 1788:

A smart repartee… will carry you through with eclat such as, ‘a miss is as good as a mile’.