Why we lack peace?

You will keep him in perfect peace, Whose mind is stayed on You, Because he trusts in You. Isaiah 26:3

Abundant peace belongs to those who love Your instruction; nothing can make them stumble. Psalm 119:165

And the peace of God, which surpasses all understanding, will guard your hearts and your minds in Christ Jesus. Philippians 4:7

So, as per the scriptures we have in front of us today, we do not lack peace and that too the perfect peace if our mind is steadfast on the Lord. 

In other words we lack peace or the perfect peace when our mind wanders from God. 

So, it is totally up to us if we want peace or not.