From the Sacred India Tarot, Death (Mara); from the State by State Playing Cards, 'Arizona/9 of Hearts:'
Though Mara is illustrated as a demon, he is simply the personification of the negative attributes of the human ego and mind. Buddha met Mara (his ego-self) when he sat under the bodhi tree to attain enlightenment. The ego-self wants to avoid all pain, enjoy all pleasure and engage in whatever relieves our boredom or restlessness. None of these are a problem unless they keep us from seeing clearly and acting with discernment when it comes to reality. Meeting life unskillfully is Mara's specialty, and he makes great use of fear, anger, longing, and other emotions to do it. Arizona's Grand Canyon is an excellent analogy for how such emotions can wear us down over time if we are constantly reacting to them rather than simply being aware of them; it is easy for the ego-self to convince us that whatever we think or feel represents the eternal truth. The Dhammapada suggests that we are like a fish flopping around on dry land when we are in reactive mode. Instead, we can live mindfully and harness the mind with insight.