Summary: Stop fretting over the prosperity of the wicked and look forward to what the Lord has in store for those who are called his children.
Psalm 37:1 (quickview) ,2 - Fret not thyself because of evildoers, neither be thou envious against the workers of iniquity. For they soon shall be cut down like the grass, and wither as the herb.
The word fret refers to the point just after a fire has been ignited when the flame is the hottest. Think about what happens when you light a match. As the head of the match is ran across the striker it ignites into a burst of flames. After the sulfur burns off and the blaze settles down the matchstick is left with a much smaller fire. That initial point after ignition is what the writer if Psalm 37 (quickview)  is warning us about. He says not to fret ourselves, or burst into a flame of emotion, because of evildoers.
That is awful hard to do because most of us have seen how unfair life can be sometimes. It always seems like those who prosper the most are the ones who also hate God the most. Why does God allow the wicked to prosper while the righteous have to suffer through life? I wish that I could answer that question. I would like to expound some great theological truth on the matter and clear it up for everyone, but I do not have that kind of knowledge. I don’t feel too bad though because I am in good company. Solomon, who was the wisest man to ever live, wrote in the book of Ecclesiastes:
Ecclesiastes 8:16 (quickview) ,17 - When I applied mine heart to know wisdom, and to see the business that is done upon the earth: (for also there is that neither day nor night seeth sleep with his eyes:) then I beheld all the work of God, that a man cannot find out the work that is done under the sun: because though a man labor to seek it out, yet he shall not find it; yea further; though a wise man think to know it, yet shall he not be able to find it.
What is he saying? He is saying that God is the one in charge of the business that is done upon the earth and it is not up to us to figure out why he does what he does. Our responsibility is to accept God for who he is and trust that he knows what he is doing. But how can we have any hope if the wicked always seem prosper while the righteous always seem to suffer? Look at Psalm 37:2 (quickview)  - For they soon shall be cut down like the grass, and wither as the herb.
Remember that God’s word is the final authority. If God says that one day the wicked will be cut down like the grass, then rest assured that it will happen. God will deal with them in a way that we could never imagine and he will deal with them in a way that is both righteous and holy.
What we need to draw from this passage of scripture is that it is a waste of time for us to wring our hands and worry over the success of those who continually speak against God. One day they will meet with him face to face and have to answer for their actions. God will repay them for their evil deeds.
We need to stop fretting over the prosperity of the wicked and look forward to what the Lord has in store for those who are called his children. The remainder of Psalm 37 (quickview)  will show us how to overcome being envious of the wicked by looking forward to the promises of God.