True peace of mind is found in your original state of SELF AWARENESS prior to and inner witness to the outer body mind and thoughts." That is, in Enlightenment, SELF-realization, Satori, Nirvana, Samadhi, at-one-ment, spiritual understanding, God-SELF-realization - rest. (Matt. 11:28)
And...to "KNOW-THY-SELF" to be eternal spirit...never ending.