We don't realize that, somewhere within us all, there does exist a supreme self who is eternally at peace. Elizabeth Gilbert
Peacefulness is an inner sense of calm - it comes from becoming still - in order to reflect and meditate on our inner wisdom and receive answers. A peaceful heart is one that is free from worry and trouble.
Happiness, true happiness, is an inner quality. It is a state of mind. If your mind is at peace, you are happy. If your mind is at peace, but you have nothing else, you can be happy. If you have everything the world can give - pleasure, possessions, power - but lack peace of mind, you can never be happy. -Dada Vaswani