Happiness is great, but, often, very situationally dependent.
Happiness is great but, often, can’t be felt when feeling other contrasting emotions.
Happiness is great but, often, when it is the goal in and of itself, the experience doesn’t measure up to the expectation.
Peace, on the other hand, doesn’t depend on the situation.
Peace can coexist with anger, sadness, and fear.
Peace has nothing to do with expectations and everything to do with accepting your internal and external circumstances exactly as they are.