The two ultimate and unseen evils are sin and flesh, and they are always working together to bring down a man. When you give in to sins, your flesh takes over and be the master of your inner person.
Nothing in this world can set you free from the sin and flesh, but only the blood of Christ. Hence, we need to live through the HS to put our flesh to death. It is not by exercising your will, by having a renewed and recreated heart, which you achieve through prayers with a contrite heart after knowing how self-centred you are in wanting to satisfy your flesh.