(Isa 26:3) says “Thou wilt keep him in perfect peace whose mind is stayed on thee”.
Your level of peace is determined by where your mind is. You see as Christians, we must understand whatever captures the mind captures the man. Show me a man/woman which sets their mind on things above, and not on things of the earth, and I will show you a man operating in peace. Conversely, show me a man/woman which spends their time thinking about earthly things, and I will show you a man which lacks the peace of God. This is the reason God spends so much time talking about our thought life in the scriptures, because He knows “As a man thinketh in his heart so is he” (Prov. 23:7). A mans’ mind is central to whether or not he will serve God with his whole heart, or whether he will serve God at all. A man is often no more than what he thinks he is; and as believers we have to bring our mind under subjection to the Holy Spirit, because we want to be what God said we could be in His word and it all starts in our head. Therefore, if we are to keep our mind on the Lord for any length of time in our daily pursuit of life, we are going to have to read it out (the word of God), write it down (the word of God), pray it in (the word of God) and work it out (the word of God must be applied to our lives daily). Thus, it’s not easy to operate in perfect peace in this life; however, it is possible because the word of God says so. We must consistently, insistently and persistently find time to meet with God daily in order to maintain the perfect peace which God speaks of.
God Bless You.