Metta-Bhavana, or "Loving-Kindness Meditation" begins with a self-reflection on the good within us. It's a gentle reminder that we already have the seed of kindness, compassion and love. We're just "cultivating it" through practice....
Begin by setting up and stable and comfortable seat. Whether on the floor or in a chair, your lumbar should feel supported, the shoulders relaxed and the face soft, some space between your upper and lower teeth with your tongue just touching the hard palate above your front teeth.
After sitting with your breath for several minutes, calming the bodymind, call to mind something you have said or done that you feel was a kind or 'good' action. It could be a time you were generous, caring, or contributed to someone's well-being. Perhaps you offered a bowl of fresh, cool water to a stray dog near your home. Perhaps you helped a child-laden mother gather up some fallen groceries. It most certainly need not be anything "big" or "dramatic."
If something comes to mind, note what feeling arises at the recollection. It may be one of relaxed joy, a soft tremble of the heart at the recollection of the simple connection through a small act of kindness. The Buddha encouraged us to water happiness by remembering it. In fact, this practice is part of the "Four Supreme Efforts" listed under "Right Effort," the sixth limb of the Noble Eightfold Path.
If a feeling of happiness does indeed arise at the remembrance of your kind action or words, simply allow yourself to 'bask' in the tender warm glow. If nothing comes to mind, then gently turn your attention to a quality you like about yourself. It can be a skill, ability, strength or character trait within yourself that you can recognize. Again, it needn't be anything big and 'special.' Perhaps you bake a really good apple pie, and maybe you like to share it with friends. Maybe you have recently mastered a new skill or maybe you're a really good listener or loyal friend.
What is beautiful about this practice is how the tradition seems to 'bend over backward' to make it available to all of us, because if you cannot recall a time you acted or spoke generously, and if you cannot think of a skill, ability or quality you like about yourself, you can simply reflect on the primal desire you have -- like ALL beings -- to be happy! The desire to be happy is good, natural, beautiful and has a sense of 'rightness' about it.
If in any of the above reflections, impatience, irritation, anxiety or fear should arise, please don't fall into negative self-talk. See if you can return to your breath, stabilize your body/mind, and then return to the contemplation free of judgment. The real heart of any meditative practice is to let go and begin again and again and again....
It doesn't matter if the mind wanders countless times in any session of practice; in the moment you recollect it, you are already 'beginning anew!' There is nowhere your attention can go to, and no length of time it can be distracted, from which you cannot simply let go, and in that very moment, begin anew!