Going through the next section of James' teaching on the tongue, the focus here is thinking about how the tongue can be so many things at different times: controlling, powerful, and unpredictable.

The "forgotten" point was to amplify the fact that to control the tongue is truly a hopeless effort without the Holy Spirit -- self-control (of the tongue) is a fruit of the Holy Spirit's work in our life:

22 But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, 23 gentleness, self-control; against such things there is no law. 24 And those who belong to Christ Jesus have crucified the flesh with its passions and desires.

The Holy Bible: English Standard Version. (2016). (Ga 5:22–24). Wheaton: Standard Bible Society.