Lack of peace (i.e. discord, dis-ease), within us or without us, is mainly due to discontentment because we lack the presence of the true and living God who brings us satisfaction and enjoyment. For this reason, love brings us peace by quenching our thirst when we drink of the living water so that we will never thirst again. Lack of peace is due to not drinking the living water because we don't set our heart and mind on God: Isaiah 26:3 says "You will keep in perfect peace all who trust in you, all whose thoughts are fixed on you! "
From this verse, we can see that Peace depends on 1) God's keeping power, 2) our trusting, and 3) fixing our thoughts on God. Fixing our thoughts on God is how we practically allow God to keep us, and how we exercise our faith to trust in Him. This will cultivate an awareness of God's presence in our life, by which no evil or sinful thought can touch us, and no accusation or oppression from the enemy can hurt us (within or without). This is how we can practically remain in peace no matter what our outward situation looks like. This is how we can "sleep in the boat", even if outside there is a storm.
Another way to put this, is that human beings were created for God's purpose. When we are outside of that purpose, we lack peace.
The purpose of God is found in Romans 8:28-30
And we know that in all things God works for the good of those who love him, who have been called according to his purpose.
For those God foreknew he also predestined to be conformed to the image of his Son, that he might be the firstborn among many brothers and sisters.
And those he predestined, he also called; those he called, he also justified; those he justified, he also glorified.
God's purpose for us individually is to be conformed to the image of the Son, and God's purpose corporately is for us to have many brothers and sisters (for God to have many sons and daughters). This conformation follows the processes of predestination, calling, justification, and finally glorification. This conformation to the image of the Son is the essence of God's love towards us, and it includes (but is not limited to) His love in sending Jesus to die for our sins.
By putting Isaiah 26:3 and Romans 8:28-30 together, we can see that if we 1) accept Christ as our personal Lord and Savior, we become His son (or daughter), we become part of a big family known as the church, or body of Christ, and gain many brothers and sisters. This is a first way that God's love brings us peace - vertical and horizontal relationships. But this is not the be all and end all - many Christians have accepted Christ and go to church, but still do not have peace, there is more we have to do. Following this, if we 2) set our heart and mind on God continually, this will enable us to trust Him and be kept by Him as we gain a sense of His presence, and we will experience peace in our daily living. This is a second way that God's love brings us peace. In doing so, 3) we will be continually conformed to the image of the Son, and will find that we are in the centre of God's highest plan and purpose for our life, and so achieve satisfaction, enjoyment and peace. This is a third way that God's love brings us peace. To illustrate this by an example. A car is meant to be driven on a road. Suppose we try and drive that car on a railroad track. The car will clunk up and down, and we can say that this car is not in peace. But if we drive the car on a proper road as intended, the car will drive smoothly. So if we live our life as our creator did not intend, we will have lots of bumps and we may even be shaken to pieces until a wheel falls off. However if we live our life as God intended, we will be on the smooth track, we will have peace. This does not mean we will never face difficulties - sometimes even a car is battered by wind, rain or hail. But as long as it is on the road, it is going to be in peace as it goes to where it has to go. And just to reiterate the point - "living our life as our creator intended", does not mean being a good person, living a good life, being a good Christian, or going to church regularly out of habit, it means we living according to 1), 2) and 3) as outlined above which is a personal relationship with Jesus Christ, fellowship with brothers and sisters in Christ, and conformation to the image of Christ by cultivating the presence and awareness of God in our daily living by continually fixing our thoughts and heart on Him.
