ruminate - vocabulary

verb

To chew over again, as food previously swallowed and regurgitated; to meditate about, ponder.

Let's start with their explication of depression, which has metastasized in the West over the past two generations. Victims can see that Griffin and Tyrrell know why they wake up exhausted and unmotivated. This alone gives hope. Somebody finally understands what has long baffled the patient—that peace eludes him even when asleep, and that psychotherapy based on ruminating about past miseries makes depression worse.

—Lou Marano “Civilization: Psychology Breakthrough” United Press International