Proverbs 24:19-20

Do not get upset because of evildoers, or be envious of the wicked, for there will be no future for the evil man; the lamp of the wicked will be put out.  

The wicked do not get away with the evil they do to others. In the short term, it may seem that they will not suffer the consequences of their deeds, but God is still in control. Their deeds are not forgotten before God, and they will have to answer for their actions. We cannot lose heart or let their actions distract us from faith in God.