The belt of truth is the foundation, and the basis, of our armor. Without it, we cannot stand before Satan's schemes, and machinations.
But in some way, it seems like it is expressed through the other tools connected to it.
The second tool is the breastplate of righteousness. A breastplate is obviously worn to protect the heart, and other vital organs.
The truth is -- all mankind is tainted in sin. Mankind is steeped in sin from the heart. Mankind's basic motivations, and inclinations, are opposed to God's word, and design.
But the truth is also -- God's design is for mankind to live in relationship with God, in love, peace, and righteousness. So, he developed a plan to deal with sin, which is the barrier to that relationship. So, he sent Jesus into the world, to die as a sacrifice for sin. Now, if people yield their allegiance to God, and appropriate by faith the results of Christ's death, their sin is forgiven, and the become a part of God's family.
They also become partners with God to proclaim that God has made a way to peace with him, and peace in life.
As this is the opposite of Satan's intentions, he targets God's family. Satan whispers lies to God's family. The more he can convince God's family to believe the lies, the more polluted their hearts become. And their actions, emanating from their hearts, are tainted with selfishness, legalism, sin, and impurity. God's family loses its effect in the world. It loses lose, joy, and peace. It becomes ineffective in its mission for God.
So, protection of the heart becomes vital. How does one put on a breastplate of righteousness?
I will suggest that since Satan seeks to poison our hearts, we make a practice to regularly renew our hearts.
There are actually several ways to renew our hearts. Regular prayer, reading, and meditation, of God's Word are a few examples. Regular meeting with like-minded people is another. Along with meeting with people, the practice of the Lord's Supper is, in particular, aimed at heart renewal. There area other practices -- eg. silence, solitude, and fasting -- the some other's recommend.
Heart renewal is important. It will protect us from Satan's tactics. (Not that he won't try. We will hear the same lies. Now, we will have a response, so the lies will bounce off our armor.) It will also feed our hearts, providing for healthy transformation into Christ's image. Our character will change. And we will become a greater asset in God's mission.