"We are in this life for the spirit to gain control over the body rather then the other way around." - James E. Faust (Ensign. Nov. 2007)
If our purpose in life is to gain control over our bodies, wouldn't that mean many of the commandments would lead specifically to that purpose. I can think of several....from the law of chastity to fasting to the Word of Wisdom. These commandments teach us the control that is absolutely essential to our mission in life.
So if our purpose is to gain control of our bodies, wouldn't Satan choose that aspect to attack? I can think of one weapon that is absolutely effective in taking away that control.
In addiction free agency is gone. Control is gone. We are at the mercy of the addiction. We don't get to make the decisions that we know will make us happy, because the addiction is constantly ruling our lives.
I wonder though, if the actions needed to overcome addiction, are the very actions which help us understand that we can control our bodies and let our spiritual side take over in our lives. Maybe those very actions, from honesty to turning our lives over to the Lord, will help anybody who wants to truly gain control over their body and thus fill their purpose in life.