In Buddhism, a practice recommended for increasing compassion and raising bodhichitta (literally, "awakened mind") is recalling that all sentient beings were our mother, our friend, our child at some point in limitless time. Whether one believes in reincarnation or not, this practice can move one to act compassionately.
I was reminded of this practice when I had the great good fortune of hearing a talk by His Eminence Terton Namkha Drimed Rabjam Rinpoche last night. He was clear and firm: "Every being without exception has been your mother, your father, your child."
I've struggled with this practice at various times -- not surprising, given the nature of my relationship with my mother. Thinking of this or that person as my mother in some past existence hasn't always aroused compassion.
It's been suggested that those of us who struggle with the practice might do well to focus on the caregiving we did receive. Even the worst mothers (or other caregivers) fed us, got up in the night when we cried and diapered us, literally wiping our butts. Maybe, like my mother, they made us birthday cakes every year. They struggled in childbirth so that we might enjoy this moment right now. Focusing on even the smallest kindness shown by a caregiver has the potential to increase our compassion if we imagine every being showed us such kindness at some time.
One of my earliest memories is of Mom rocking me to sleep, singing. Everyone else was in bed, so clearly it was late at night. Still, she sang. I remember well the comfort of the embrace, her patting me on my little back as she rocked and sang. She might have missed a lot of opportunities to be a "good" mother later on, but that night she was kind and nurturing. Thank you, all my mothers, for this kindness. May it be returned to you 1,000 times over.