How do humans accomplish God’s will? James tells us that human anger can never bring about God’s will, and he has to be speaking here into (at least) the zealot option of the 1st Century. The Zealots, if you remember, believed God’s will was so urgent that violence was necessary. Notice these words of James:

19 My dear brothers, take note of this: Everyone should be quick to listen, slow to speak and slow to become angry, 20 for man’s anger does not bring about the righteous life that God desires. 21 Therefore,
get rid of all moral filth and the evil that is so prevalent and humbly
accept the word planted in you, which can save you.

There is a qualitative comparison at work here:

Human anger vs. Divine righteousness.

And the use of the present tense (“does not bring about”) gives one the impression that the entire scene is being sketched before our very eyes: this is not the way to bring about that.

What is God’s will/righteousness here? The NIV’s (quoted above) “righteous life” makes this a little too individualistic (and only individualistic). The best way to describe the righteousness James has in mind can be seen in three passages: James 1:22-27, 2:1-4 and 3:13-18. Good deeds, compassion and justice for each person, and peace.

Anger, even violent behaviors, will never bring about these things.