Why do we find it hard to be at peace with ourselves, each other and the world? Imagine a lake that is flat and calm and pure - it is so clear you can see the bottom. Even when the wind blows it only ruffles the surface. All is still and peaceful in its depth. Then the first polluting chemicals of the new factory and farm come rolling down the hill and into the water. Immediately it starts to cloud over and bubble a little. Chemical reactions are taking place and the purity is lost. When purity is lost peace is lost.
It is the same with human consciousness. We are innately peaceful beings. Peace is our deepest inner state of being, our true nature. To be at peace is to be in our natural state, but only when our consciousness is pure and clean and true. As soon as the pollutants of any negative images are allowed in, or we allow old memories and experiences to disturb us into negative thinking, our purity and therefore our inner peace are gone. It's not the external event or person that takes our peace away - it's because we give them permission to enter and give them life in our minds.
Keep your mind and heart free of all pollution, and peace will always be with you.