But he answered and said, It is written, Man shall not live by bread alone, but by every word that proceedeth out of the mouth of God.
Matthew 4:4 (KJV)
Just as our physical body requires physical food in order to be strengthened, so too our born again spirit requires spiritual food in order for us to reach our full potential in Christ. We are being spiritually fed anytime we receive the Word of God, when we meditate on it, and take it into our hearts. The more that our spirit is fed, the stronger it becomes. And when our spirit is strong, our ability to be victorious over the flesh increases.