Isaiah 26:3: Thou wilt keep him in perfect peace, whose mind is stayed on thee; because he trusteth in thee.
People run after many things to attain peace. Some run after meditation and yoga whereas some just take off to some vacation spots for fun and for some peace. All these are not the perfect things of peace for a child of God. In times of trial and confusion, we all have one place to go to, i.e., Jesus.
Jesus told in John 14:27″Peace I leave with you; my peace I give you. I do not give to you as the world gives. Do not let your hearts be troubled and do not be afraid.” He does not intend to give us peace like how the world gives. Peace from the world is temporary, but the peace which Jesus gives will stay in us and change our troubled situation. We will never be afraid again. If you want to have perfect peace, there is one condition. That condition is your mind should stay on God or be in tune with thoughts of God. We should always subject our mind to obey God. Every thoughts should be made captive to the mind of God.
We should constantly think of what God thinks is right and pure. In so doing, our mind will work with the mind of God. When we get distracted to the things of the world, our heart gets depressed and we feel low. On the other hand, if we let our minds to stay focussed on the things of God, we will be rejuvenated. The things of God will stay forever, that is why peace which comes from God will never let our hearts be troubled.