English Basic Explanation - Chapter 38
The opening verse of Psalm 38 informs us that David composed it "Le'hazkir" (literally, "to mention"), which the commentators explain to mean that it should be sung or recited during times of distress. According to Rashi, David intended this chapter to be recited during periods of national crisis and misfortune, whereas the Radak views it as a prayer for times of personal hardship.
David describes here the physical pain and suffering that he (or the person that will recite this Psalm) endures as a result of the "arrows" (verse 3) thrust at him by God due to his transgressions. The first half of this Psalm depicts in great detail his distress and anxiety, as well as the "burden" of sin that weighs heavily on his back. It thus refers to a situation of grave crisis and danger that the individual confronts while recognizing his unworthiness and spiritual failings, which only intensifies his fear of what the future might hold.
In the second half of this chapter (12-23), David proceeds to describe the attitude of his peers to his plight, and his response to them. He is abandoned by his comrades and taunted and deceived by his foes. But rather than respond, David chooses instead to remain silent and speak only in prayer to God, in the hope of securing His assistance and protection.
This Psalm beautifully expresses the message that the Rambam famously develops in the beginning of Hilchot Ta'aniyot, that situations of danger and crisis must be met with sincere introspection and repentance. A person must recognize that when crisis strikes, it occurs not coincidentally, but rather as the Almighty's response to our sins. The individual for whom this chapter was composed faces grave danger and acknowledges that his wrongdoing caused or at least contributed to the dire situation he confronts. However, rather than despair, he places his trust in God and His compassion, confident that Teshuva and heartfelt prayer have the capacity to permanently extricate him from his troubles.