Why do I become Jealous?

 James 4:1 What causes fights and quarrels among you? Don’t they come from your desires that battle within you?

It is sad that there are selfish desires battling in me. They could be so many that these desires battle in me seeking to be satisfied before the others. The desires are selfish in themselves and they are born from my selfish nature.

Verse 2 You desire but do not have, so you kill. You covet but you cannot get what you want, so you quarrel and fight. You do not have because you do not ask God.

I desire and kill-Wishing something was mine. Since the owner is still alive, it can only change ownership if the person 'dies'. We 'kill' by selfish desires.

Luke 20: 9-16
9 He went on to tell the people this parable: “A man planted a vineyard, rented it to some farmers and went away for a long time. 10 At harvest time he sent a servant to the tenants so they would give him some of the fruit of the vineyard. But the tenants beat him and sent him away empty-handed. 11 He sent another servant, but that one also they beat and treated shamefully and sent away empty-handed. 12 He sent still a third, and they wounded him and threw him out.

13 “Then the owner of the vineyard said, ‘What shall I do? I will send my son, whom I love; perhaps they will respect him.’14 “But when the tenants saw him, they talked the matter over. ‘This is the heir,’ they said. ‘Let’s kill him, and the inheritance will be ours.’ 15 So they threw him out of the vineyard and killed him. “What then will the owner of the vineyard do to them? 16 He will come and kill those tenants and give the vineyard to others.”When the people heard this, they said, “God forbid!”

This is the parable of the tenants who beat up the servants of the vineyard's owner. But when he sent his son, they killed him.

Verse 14. The reason they killed him was to take over the vineyard.
Desiring something that has an owner is equivalent to wishing them dead.

Instead of jealousy, God commands:

1. Submission to God and resistance to the devil. James 4:7 Submit yourselves, then, to God. Resist the devil, and he will flee from you. 
2. Drawing near to God. James 4:8 Come near to God and he will come near to you. Wash your hands, you sinners, and purify your hearts, you double-minded. 
3. Humility-James 4:10 Humble yourselves before the Lord, and he will lift you up.
4. Stop slander-James 4:11 Brothers and sisters, do not slander one another. Anyone who speaks against a brother or sister[d] or judges them speaks against the law and judges it. When you judge the law, you are not keeping it, but sitting in judgment on it.