that's really bad when people wants to have same thing from other people or wants to be have more than the other person have.
Jealousy is not bad at all.
Few people become successful due to their jealousy of those people who achieve things.
So,they also tried to do their best to achieved what other people achieved.
Jealousy only becomes bad when you want to get what your neighbors have..like robbery,it is the result of bad jealousy,taking other's belonging.