Throughout the entire year, a person should always look at himself as equally balanced between merit and sin and the world as equally balanced between merit and sin. If he performs one sin, he tips the balance and that of the entire world to the side of guilt and brings destruction upon himself. [On the other hand,] if he performs one mitzvah, he tips his balance and that of the entire world to the side of merit and brings deliverance and salvation to himself and others. This is implied by (Proverbs 10:25
) ‘A righteous person is the foundation of the world,’ i.e., one who acted righteously, tipped the balance of the entire world to merit and saved it.