Joy is being willing for things to be as they are.
Body tension will always be present if our good feeing is just ordinary, self-centered happiness. Joy has no tension in it, because joy accepts whatever is as it is.
We learn in our guts, not just in our brain, that a life of joy is not in seeking happiness, but in experiencing and simply being the circumstances of our life as they are; not in fulfilling personal wants, but in fulfilling the needs of life.