Isaiah 26:3 NKJV
You will keep him in perfect peace, whose mind is stayed on You, because he trusts in You.
Here is a key to staying in perfect peace - keeping our minds on the Lord. As long as we can keep our minds on the Lord, we can stay in perfect peace. We cannot do that easily. We must become very familiar with God's Word, His character and His superior ability. When we think about someone, the length of time our minds can stay on that person is based on how much we know about them. It is based on what we know they would think or say about our situations. If we know little about them, we can spend only a little time thinking about them. If we now a lot about them we can think about them for a long time. When we are tempted to worry, we can keep our minds on the Lord if we know what He had to say about our situation and are convinced that His Word to us is good. It's like Peter walking on the water. He was able to walk on the water as long as he focused on what Jesus said ("Come"). When he began to question the power of the storm over Jesus' words, he lost his peace and began to sink. If we are not in the "perfect peace, constantly" stage, we need to grow in the areas of knowing what the Lord said by studying His Word. We also need to fellowship with Him to get to know His dependability and the superiority of His power.