What are the obstacles to the practice of loving-kindness (metta)?

The practice of loving-kindness (metta) starts with oneself.  We cannot be kind or forgive others if we are not kind and forgive ourself.  By learning to be kind and to forgive ourself for the defilements (ignorance, ill will and greed) that lie in the depths of the mind, we will be learning how to be kind and forgive others for their defilements.  Kindness and forgiveness of ourself and of others happen simultaneously, when we are kind to ourself we will be kind to others and when we are kind to others we will be kind to ourself.

The obstacle to the cultivation of loving-kindness is the egoic consciousness.  The egoic consciousness is the personality or false self and is composed of the five clinging aggregates: material form, feeling, perception, mental formations and sense consciousness.  The ego is maintained and is nurtured by assuming a superior stance; that is, by putting others down with judgement and criticism, and is highly critical of oneself: the ego judges layers of the psyche that appears apart from itself.  The ego judges others and oneself in order to maintain its fragile impermanent sense of self and to grow larger.  Other aspects of the ego is its tendency to be in a constant state of war, violent towards oneself and others, and it is also nurtured with negative attitudes such as depression, having a victim mentality, irritation, frustration, etc.  By understanding and maintaining mindfulness of the behavior of the ego, one gradually learns how to be free of the influences of the ego.

The behavior of being judgmental and critical of ourself and of others is not beneficial or supportive to the cultivation of peace, happiness and loving-kindness.  The experience of peace and happiness grows in proportion to the degree that we are liberated from the impulses, reactions and tendencies of the ego.  Liberation from the ego is the priority and the purpose of spiritual practice.  Living and acting in the world is the medium by which the mind is trained by means of spiritual practice to tame the ego, by first becoming aware of the behavior of the ego and then to resist egoic reactions.  The mind is trained to create a space or pause upon awareness of initial egoic impulses and tendencies, so that one will have the free will to respond with skillful and wholesome thoughts and actions.

The ego has been the master over the mind for thousands of lifetimes and have grown to be  intelligent and clever in maintaining control over the mind.  Libration from the ego requires dedication to the study and practice of the Four Noble Truths and the Noble Eightfold Path, which are the principal teachings of Lord Buddha; and also requires that wholesome and skillful mental faculties be developed such as: energy, mindfulness, concentration, patience, loving-kindness, forgiveness, and the ability to let go of the unwholesome states of mind.

Frustration, impatience and negativity are the behavior and symptoms of the ego.  Watch out for them and when detected, regain your mindfulness and exert energy and focus to bring forth wholesome states of mind.  Never give up!  The Buddha and his Noble disciples are our examples that liberation is possible and can be experienced here and now.  Spiritual friends are our support for staying on the righteous path.

Each and everyone of us in the world have defilements and we are all doing our best.  The path through life in which we develop wholesome qualities are supportive by associating with spiritual friends.  It is our duty to be a spiritual friend to others and to oneself.