You will keep in perfect peace those whose minds are steadfast, because they trust in you. Trust in the Lord forever, for the Lord, the Lord Himself, is the Rock eternal. Isaiah 26:3-4
Sometimes, even the mind of a TRUE believer will drift into an area that is not conducive to righteousness, and it can cause that TRUE believer to transgress against God.
The mind is a fertile place, where sinful thoughts and deeds are conceived, and from the mind to the heart sins are birthed, and the individual is brought to the place of decision making, to either follow their mindset and the desire of their heart or to set their mind on Jesus Christ, and the things of God and do all they can to KEEP their mind STEADFAST on Godly things.
When a person has a TRUSTING heart it enables them to have a STEADFAST mind. And because they TRUST in God, it becomes easier to have that STEDFAST mind. The Prophet Isaiah encourages us to TRUST in the Lord FOREVER, because He is our Rock eternal. Continually TRUST Him because He is FIRM as a rock and will not be weakened or wasted away by anything. He is TRULY the rock on which we stand, ALL other ground is SINKING sand.
If you have not turned your HEART and MIND over to God, then you are standing on that SINKING sand. And you are in grave danger of SINKING into that abyss known as Hell, the place of torment, torture, misery and pain for ALL eternity. However, God in His infinite MERCY and GRACE is giving you the opportunity to change your destination by: CONFESSING your sins to Him and asking Him for His FORGIVENESS, BELIEVING, with ALL your HEART, that Jesus died for YOU, and is ALIVE in Heaven, making intercession for you, before God, then ACCEPT His gift of SALVATION and have a STEADFAST mind and a TRUSTING heart and a PEACE that passes ALL understanding. Do it NOW, while you still can. He's waiting and coming SOON!!!