Rick Hanson provides a good summary of the third noble truth of the Buddha, that we can realize the end of suffering by letting go of the causes of our distress and thus beginning to experience equanimity. You can find his article here: The Third Noble Truth-The Noble Truth of the End of Suffering
Thanissaro Bhikkhu has a detailed description of the third noble truth and the way that the Buddha described it in a chapter from his book on the Buddha’s teachings on the four noble truths. Realizing the third noble truth results from letting go of clinging. This letting go leads to unbinding and release and the end of suffering. You can find that chapter here: The Third Noble Truth