Thomas Brooks emphasizes the importance of recognizing and repenting for both great and small sins, as highlighted in Psalms 19:12. He points out that while many may lament over significant transgressions that impact their reputation or well-being, they often overlook the subtler sins such as wandering thoughts and self-confidence. True godly sorrow encompasses a deep awareness of all sins, regardless of their perceived magnitude, and leads to a heartfelt plea for cleansing from secret faults. Brooks encourages believers to cultivate a sensitivity to these 'gnats' of sin that can easily be ignored yet are detrimental to one's spiritual health.