Often Zen Master Seung Sahn says, "If the direction of your life is clear, then your whole life is clear. If your direction is not clear, then your life will always be a problem." The reason we practice Zen is to understand ourselves completely, attain our original nature, and save all beings from suffering. This is our direction - the original job of all human beings. In this there is no "I, my, me." If we have "I, my, me" then we will get suffering, guaranteed.
Several years ago at the end of the long winter retreat in Korea, Byoek Am Sunim, our precepts teacher, gave each of the participants a calligraphy It read: "You make, you get." This is a very simple equation! At that time, someone asked him why it was that people suffer. He said, "Human beings continue to suffer because they do not see cause and effect clearly." So, the question "Why do I suffer?" has a simple answer: "What do you want?"
Achaan Chah, a now-deceased meditation teacher in Thailand, would often walk around the monastery grounds and ask every monk that he met, "Are you suffering today?" If the monk answered "yes," Achaan Chah would say, "Oh, then you must have a lot of desires today." If we can clearly see the nature of desire and anger, then it is possible to let them go. This means seeing cause and effect clearly. However, one more step is necessary.
One time a monk came to Zen Master Seung Sahn and said that he wanted to stop being a monk because the monk's life for him was a living hell. Zen Master Seung Sahn replied, "If your direction is clear, then even living in hell is not a problem." This means if you want to help this world, then even suffering should not be a hindrance. Most important is direction. If your direction is clear, then the suffering you experience becomes "Big Suffering" and helps this whole world. So, what do you want?