There is a new fortress within you and the Holy Spirit is a witness to it. This fortress you have is the mindset you have built on Christ. This cannot be shaken or destroyed and neither will it decay over time. The power, workings, promises, and blessings of God are dependent on this new and improved foundation to whatever you do and speak.
Romans 12:2 (AMP) - “And do not be conformed to this world [any longer with its superficial values and customs], but be [a]transformed and progressively changed [as you mature spiritually] by the renewing of your mind [focusing on godly values and ethical attitudes], so that you may prove [for yourselves] what the will of God is, that which is good and acceptable and perfect [in His plan and purpose for you.”