You have a point about unforgiveness resulting in a lot of heartache; yet it seems to me that Christians with the deepest, cleanest sincere faith don’t get significantly less colds or flus than atheists do. Still, it bothers them less because they are living in a generous stream of grace. Also forgiveness presupposes grace to forgive. When one is all hung up on oneself or the world, there isn’t much if any of that.
Yes...and repressed anger does indeed cause all sorts of dis-ease.