Do you not know that when you present yourselves to someone as slaves for obedience, you are slaves of the one whom you obey, either of sin resulting in death, or of obedience resulting in righteousness? But thanks be to God that though you were slaves of sin, you became obedient from the heart to that form of teaching to which you were committed.
No one is a free agent!
"You are slaves of the one whom you obey." Once you choose your life principle, you are bound to it. If you decide that pleasing yourself is the guiding principle of your life, then your own passions and desires will rule you. Just try to buck those passions and desires and you will see the truth of this passage.
On the other hand, if you decide that pleasing God is the guiding principle of your life, then God's word will rule you. You will go to His word because it is there that you find out what pleases Him. As you do what pleases Him, His pleasure will give you pleasure. You will know the freedom of making God your master.
There is no better life than the life you live with God, not yourself, at the center of it. That is why you must recognize that the one true freedom you have is the freedom to choose your master. Choose wisely.