In Gita god has told us about the gates of hell. Lust, anger and greed. What are each one of them? Why are they bad?
Lust and greed are simply desire for worldly things. Gita itself answers the question why lust, greed and anger are bad.
In one who dwells longingly on sense objects, an inclination towards them is generated. This inclination develops into desire, and desire begets anger.
Anger generates delusion, and delusion results in loss of memory. Loss of memory brings about discriminative intelligence, and loss of discriminative intelligence spells ruin to a man.
A man of disciplined mind, who has his senses under control and who has neither attraction nor aversion for sense objects, attains tranquillity, though he may be moving amidst objects of the senses.
On attaining tranquillity all one's sorrows come to an end. For soon does the intellect of a tranquil person becomes steady.