"For instance, even in the rock-hardness of rage, if we look below the surface of the aggression, we’ll generally find fear. There’s something beneath the solidity of anger that feels very raw and sore. Underneath the defensiveness is the brokenhearted, unshielded  quality of bodhichitta. Rather than feel this tenderness, however, we tend to close down and protect against the discomfort. That we close down is not a problem. In fact, to become aware of when we do so is an important part of the training. The first step in cultivating loving-kindness is to see when we are erecting barriers between ourselves and others, The compassionate recognition is essential. Unless we understand - in a nonjudgmental way - that we are hardening our hearts, there is no possibility of dissolving that armor. Without dissolving the armor, the loving-kindness of bodhichitta is always held back. We are always obstructing our innate capacity to love without an agenda.
So we train in awakening the loving-kindness of bodhichitta in all kinds of relationships, both openhearted and blocked. All these relationships become aids in uncovering our ability to feel and express love."
Pema Chodron, The Places That Scare You: A Guide to Fearlessness in Difficult Times.