Divine peace has an inner and outer manifestation. Exteriorly, it manifests as fire, as zeal, as transformation, as death and rebirth. Interiorly, it manifests as silence, as knowledge, as joy, as union with the Beloved: a joy of union that is capable of communicating itself to others.
I have found that the greatest degree of inner tranquility comes from the development of love and compassion. The more we care for the happiness of others, the greater is our own sense of well-being. Cultivating a close, warmhearted feeling for others automatically puts the mind at ease.