Fasting is not a sign of how righteous we are. Fasting is a sign of how broken things are. It is a recognition and reflection of the brokenness of the world and our need for God. Jesus rightly connects it with mourning, and it is appropriately observed by sinners in true repentance and dependence upon Him. Disconnected from its substance, it becomes nothing more than an external religious display. But when we seek God in the type of fasting that He accepts, that fast will be turned into a feast.