Separation is the great illusion, the belief that you are a fragment cut off from the whole. All suffering grows from it. It is undone not by thinking your way to unity but by a kind of dying, the surrender of the small separate self the cross has always stood for.
When that false center gives way, the division falls apart. Earth and heaven, the self you defended and the God you longed for, are one undivided whole. Peace is not something added. It is what remains when the sense of separateness dies and the wholeness that was always there is recognized.