The Human Brain
The human brain evolved with a tendency toward noticing what is wrong more than what is right. It was more important for us to remember that the bear lived in a certain neck of the woods than to remember that if you sit out on a certain rock at a particular time of day, you may have a wonderful esthetic experience of the sunset. This helped us survive as a species. The vast majority of this negative material no longer has survival value, but still warps our awareness in a negative direction, causing us to see the world as more dark and difficult that it actually is.
Fortunately for us, we know that the brain is plastic—meaning, we can shape our awareness. Whatever we tend to think and reflect on, that becomes our tendency. This is the message both of modern neurology and psychology, as well as the observation of the Buddha 2600 years ago. Because of this, we can train ourselves to focus more on what is good. For example, this simple practice of writing down several things we are grateful for several times a week has a positive effect on our mood and general outlook. This is the practice of mindfulness of what is wholesome. A wonderful form of this practice is mindfulness of kindness. Unkind and inconsiderate acts stand out for us precisely because they are unusual. But if you begin to notice the small acts of kindness you encounter every day, from someone holding a door for you or someone else to the simple smile of a clerk at the store, you can help create a more positive reality for yourself and others.