And [Jesus] came to the disciples and found them sleeping, and said to Peter, `So, you men could not keep watch with Me for one hour? Keep watching and praying that you may not enter into temptation; the spirit is willing, but the flesh is weak'.
Your spirit is willing; it wants to do what is right, to be pleasing to God. But your flesh is weak; you often find yourself unable to resist temptation, to live God's way!
In order to be able to live the godly life you desire, you must be "transformed by the renewing of your mind." You must use the tools God has given you to renew your mind. As Jesus says to Peter, one of the most significant tools He has given us is the tool of prayer.
As you begin spending time talking to God, focusing on your relationship with Him, taking the issues of life to Him, things begin to change. You find yourself more concerned with the things of God; you start placing more value on spiritual things; you find yourself caring less about the temptations of this world.
Don't sit around moping because you can't seem to change; and don't sit around waiting for God to change you some day. Pick up the tool of prayer that God has given you and start renewing your mind. The next thing you know, you will be experiencing "transformation"!