To develop understanding, you have to practice looking at all living beings with the eyes of compassion. When you understand, you love. And when you love, you naturally act in a way that can relieve the suffering of people.
Understanding and love are not two things, but just one. Suppose your son wakes up one morning and sees that it is already quite late. He decides to wake up his younger sister, to give her enough time to eat breakfast before going to school. It happens that she is grouchy and instead of saying, "Thank you for waking me up," she says, "Shut up! Leave me alone!" and kicks him. He will probably get angry, thinking, "I woke her up nicely. Why did she kick me?" He may want to go to the kitchen and tell you about it, or even kick her back. But then he remembers that during the night his sister coughed a lot, and he realizes that she must be sick. Maybe she has a could, maybe that is why she behaved so meanly. He is not angry anymore. At that moment there is Buddha in him. He understands, he is awake. When you understand, you cannot help but love. You cannot get angry.
~Thich Nhat Hanh