Inner man.

EPHESIANS 3:16
...that He would grant you, according to the riches of His glory to be strengthened with power through His Spirit in the inner man.

Real strength is found in what Paul called "the inner man." He understood that life is to be lived from within the inner man. To be strengthened through God's Spirit in the inner man is to experience the  ministry of the Spirit of Christ within us, living each moment in recognition that He alone is our source of life.
  It's from the inside that the indwelling Christ will transform you. It's so easy to get it backward. Legalistic religion seeks to reform us from the outside, stressing that if we will simply behave in certain ways we will be changed. The effect of legalism is always the same. Jesus said people might clean up well on the outside, but on the inside, still be full of filth.
  Refuse to fall into the self-help perversion of grace that would tell you that you need to improve what you do outwardly to facilitate inward change. The indwelling Christ is capable of  hanging you from the inside out. Protect and nature your inner life, and outward actions will fall into line