Central to any spiritual practice is the cultivation of love and compassion towards ourselves and others.  This is where our practice begins to really come alive, where the proverbial rubber meets the road, bringing our practice out of our head and into our heart.

In Buddhism cultivating an awakened heart is a central teaching.  According to the teachings of the Buddha, metta is the first of a group of four related concepts that indicate four attitudes of mind necessary for social well-being and individual peace.

Compassion accepts others as they are. One who thoroughly realizes compassion no longer sees any separation between self and others. Compassion is the wholesome and spontaneous response to all situations.
— Tarthang Tulku

All these four taken together are called the Brahmavihara, Sublime States or Four Immeasurables:  

1. Loving-kindness (Pali: metta, Sanskrit: maitri) towards all: the hope that a person will be well; the wish that all sentient beings, without any exception, be happy.

2. Compassion (Pali/Sanskrit: karuna) towards the suffering of others. The wish for all sentient beings to be free from suffering.

3. Altruistic joy (Pali/Sanskrit: mudita) or unselfish joy, the pleasure that comes from delighting in other people's well-being rather than begrudging it.

4. Equanimity (Pali, upekkha, Sanskrit, upeksha) is evenness of mind, unshakeable freedom of mind, a state of inner equipoise that cannot be upset by gain and loss, honor and dishonor, praise and blame, pleasure and pain.

In Mahayana Buddhism, compassion (karuna) is one of the two qualities, along with enlightened wisdom (Sanskrit: prajna), to be cultivated on the bodhisattva path. Moved by compassion, Bodhisattvas take the vow to liberate all sentient beings from suffering, including ourselves. By offering love, kindness, compassion and joy to ourselves we cultivate a softness and gentleness that we can then extend to others more easily. This can help us to overcome our self-centered outlook and cultivate deeper compassion and wisdom. 

Guided metta Meditation