Isaiah 26:3

You will keep in perfect peace all who trust in you, all whose thoughts are fixed on you!

From the New Life Study Bible:

We can never avoid strife in the world around us, but when we fix our thoughts on God, we can know perfect peace even in turmoil. We focus our mind on God and his Word, we become steady and stable. Supported by God’s unchanging love and mighty power, we are not shaken by the surrounding chaos. Do you want peace? Keep your thoughts on God and your trust in him.