To me the phrase "I'm living my life through him/her" carries with it a sense of withdraw. A sense of dreams not realized. I recognize not everybody can be what we dream to be due to lack of a particular skill, talent, resource, or drive to perform in the position. And I acknowledge that like John Donne said, "No man is an island." and we need supporters in every facet of life. However, for the Christian, God asks the Believer to go a step further.
Where the human supporter is limited in living our life through somebody or some cause, Father God has infinite resources to supply through His Followers to make a difference in this world for His Glory. God's Way is not a matter of mere talk; it's an empowered life. (1 Corinthians 4:20) If The Body of Christ, The Church, ever gets a firm grasp on this concept - look out world. The body is a unit, though it is made up of many parts; and though all its parts are many, they form one body. So it is with Christ. (1 Corinthians 12:12) If The Church of the Living God ever gets past all of what has created the denominations and divisions to begin with then maybe God can more effectively Live Through His Church as a unified Body.
Until then we must recognize that an empowered life comes from a source of power. If your source of power comes from yourself, then that is weak and limited. However, if your are continually plugged-in to Christ, as a Christian should be, you know The Source is Almighty and never-ending. Jesus said, "I am the vine; you are the branches. If a man remains in me and I in him, he will bear much fruit; apart from me you can do nothing. (John 15:5) Instead of living our lives through someone else, let us daily seek God's Way lived out through us as we stay connected, through God's Word and prayer, to be used as An Empowered Life.