The human mind and heart has the capacity for compassion, which produces important ramifications for cooperation. These are the results of experiments by David DeSteno and others discussed in today's NY Times, "Compassion Made Easy."
Interestingly, there are environmental triggers and positive externalities to this practice. The environmental triggers for feeling compassion could be simple things that bring two people randomly together. Once compassion is triggered, it spreads to third parties. This is reminiscent of the oxytocin findings by Paul Zak, who has a theoretical model to explain the results.
If you are not doing active work on becoming compassionate in your life, as encouraged by virtually all major religions and psychological groups such as AA, you may be missing a key element for creating a fulfilled life. Adam Smith's superior prudence likewise presupposes "the best head joined to the best heart."