Do not covet your neighbor’s house. Do not covet your neighbor’s wife, his male or female slave, his ox or donkey, or anything that belongs to your neighbor.
Exodus 20:17 HCSB
This is one of the ten commandments. To covet is the opposite of being content. Godliness with contentment is a great gain (1 Timothy 6:6 HCSB). Desiring what some one has, is the result of thinking the grass is greener on the other side. As most of us have learned from experience, it's not.