There's a strange verse in Bamidbar 21:27, "Therefore the MOSHLIM (poets) would say,' Come to Cheshbon; let it be rebuilt and established as the city of Sichon.' "

The Ramban explains that this poem is quoted as proof that Cheshbon had become a city of Sichon. After Sichon's victory, let Chesbon be rebuilt as the capital city of Sichon after it was destroyed in battle.

The Torah is not ancient history. The Torah is G-d's own personal GPS for us how to travel on the path of life. So why should we care about some ancient and long forgotten battle between pagan kings and its consequences? 

Therefore the Talmud  Bava Basra 78 understands this verse differently. The Talmud explains that the word, MOSHLIM in our verse is the plural of the word MOSHEL, a ruler. In the context of our verse the word MOSHLIM refers to people who rule over themselves by controlling their Evil Inclination. The word CHESHBON in our verse really means "a reckoning" which means soul searching.

Our verse is understood by the Talmud to be the words of those who control their passions and who are not controlled by their Evil Inclination. Those persons say, "Let us make a reckoning of the world, the loss that a Mitzva entails against its reward, and the gain from a sin against the loss it brings."

In order to grow and progress spiritually in life, one must triumph over the formidable challenges, presented by the Evil Inclination. The key to our success in defeating the Evil Inclination is by making a CHESHBON, assessing what one gains and what one loses by all one's actions, whether good or evil.  As the Mishna  states in Avot, "Who is wise? One who forsees  the consequences of his actions and behavior." When one performs a Mitzva, the loss, if there is one, is temporary and miniscule in comparison to the eternal reward one receives. For a sin, the pleasure is fleeting and quickly forgotten. The loss, entailed by the sin,  in contrast, is suffering in the Afterlife.

Our task in life is to constantly make this CHESHBON, introspection, soul searching and reckoning. Many people tend to ignore this formula for success on our long and winding road through life. The reward of making the right CHESHBON is Eternal Life and happiness in OLAM HABA.