We fail because we are trying to bring about change for the wrong reasons and using the wrong methods.

Romans 12:1-2 - Our bodies are a living sacrifice and they do not belong to us. (1 Corinthians 6:19)

God gave us the perfect vessels to accomplish His will. We abuse them, with not taking care of our bodies, leaving ourselves less capable of doing all that God has called us to do.

Response to thought: We need to undergo a transformation in the way we think about ourselves as humans.

If I take care of my car to make sure I can drive, or my glasses so I can see, or even make sure my computer has antivirus software and the updates are current, why wouldn't I be more diligent in taking care of the tool God created to accomplish His will through me?