Fret = worrying. Instead of worrying about things we have no control over, we should delight ourselves in the Lord, and he will make our paths straight.
Commit your way to the Lord;
trust in him and he will do this:
6 He will make your righteous reward shine like the dawn,
your vindication like the noonday sun.
7 Be still before the Lord
and wait patiently for him;
do not fret when people succeed in their ways,
when they carry out their wicked schemes.
8 Refrain from anger and turn from wrath;
do not fret—it leads only to evil.
9 For those who are evil will be destroyed,
but those who hope in the Lord will inherit the land.