You can clearly see that much of the unhappiness that we experience in life is due to errors of human intelligence: we don't analyze situations correctly so we experience negative emotions. To overcome negative emotions, we have to become aware of their long-term and short-term consequences. We also have to analyze the reality of the situation. Reality is made of interdependent parts. Things happen because of many causes and conditions. That is reality. But in our mind, in our perception, if some unhappy things happen, we point to one cause and blame it. Then we develop anger. But if we think more carefully, if we are realistic in our assessment, we know these things happen because of many causes and conditions, which include one's mental attitude. Therefore, if we know that in reality, there are many causes, we won't blame a single factor. - The Dalai Lama, Many Ways to Nirvana