The greatest victory we can accomplish in this life is to overcome
the sins of our flesh and this can only be done through the Divine
assistance (grace) of the Lord Jesus Christ.
We are all locked into battle between our spirit which is willing to
do the will of God and the flesh which is weak and yields easily (too
easily) to the wiles of the devil.
Brethren, this is what is meant by the scripture when it speaks of
overcoming the world (our own sinful flesh).
John said, who is he that overcomes the world but he who believes
that Jesus Christ is the Son of God.
Faith and repentance (the willingness to turn from our own ways
towards God's way and actually doing it) is the victory that
overcomes the world.
He who conquers his own tongue is greater than he who can conquer a
city.