Regret too can be grounded in an understanding of the results of our misdeeds, which is rebirth in the three lower realms—the animal, hungry ghost and hell realms. These three correspond to the three main delusions of ignorance, attachment and anger, respectively. We can perceive animals directly, but people often express skepticism about the remaining two realms. Yet His Holiness suggests that we do not need to see them directly, for it is sufficient to observe our own minds when under the power of attachment and anger. This alone offers a glimpse of what the hungry ghost and hell realms are like. For example, when we burn with anger, we can see how anger consumes us like the fires of hell consume those who live there.

~Karmapa - 28TH KAGYU MONLAM: DAY THREE

http://the17thkarmapa.blogspot.tw/2012/07/28th-kagyu-monlam-day-three.html