Peace is the absence of conflict, a state of untroubled, undisturbed believing. The Christian is to learn to walk by faith in God (believing) and not only by what appears obvious. The information in the world is not always reliable, but God's Word is truth, and therefore constantly accurate. Believing the Word of God produces peace (Romans 15:13), whereas entertaining doubts and fears results in unbelief and causes mental turmoil.
God's Word is absolute, and always comes to pass. It is trustworthy and reliable. This gives the believer rock-solid confidence, and therefore strength. Strength and peace go hand in hand. "The Lord will give strength to His people; the Lord will bless His people with peace." (Psalm 29:11)
Jesus could sleep through a storm, totally trusting in God. Peace is a calm state of mind, resting in God's care, not upset by the chaos of the world. Jesus acknowledged that the world offers no real peace because it is ruled by the god of this world, Satan. Only an intimate relationship with the Lord Jesus Christ can bring real peace. "Peace I leave with you, My peace I give to you; not as the world gives do I give to you. Let not your heart be troubled, neither let it be afraid." (John 14:27)
Colossians 3:15 says "Let the peace of God rule in your hearts." This state of tranquility should be the norm for a believer walking by the Spirit, and any turbulence should be cause for alarm and attention. "For God is not the author of confusion but of peace, as in all the churches of the saints." (1 Corinthians 14:33) It is essential to stay focused on God and the truth of His Word, trusting Him. "You will keep him in perfect peace, whose mind is stayed on You, because he trusts in You." (Isaiah 26:3) Awareness of God's presence and living with God's power gives confidence, and therefore peace.
"Oh, that you had heeded My commandments! Then your peace would have been like a river, And your righteousness like the waves of the sea." (Isaiah 48:18)