How rummination can both help and hinder.

Altamirano et al. do a simple study that shows that depressive rumminators (like myself?) are more stable in maintaining goals, but sacrifice flexibility:

Although previous research suggests that depressive ruminators tend to become stuck in a particular mind-set, this mental inflexibility may not always be disadvantageous; in some cases, it may facilitate active maintenance of a single task goal in the face of distraction. To evaluate this hypothesis, we tested 98 college students, who differed in ruminative tendencies and dysphoria levels, on two executive-control tasks. One task emphasized fast-paced shifting between goals (letter naming), and one emphasized active goal maintenance (modified Stroop). Higher ruminative tendencies predicted more errors on the goal-shifting task but fewer errors on the goal-maintenance task; these results demonstrated that ruminative tendencies have both detrimental and beneficial effects. Moreover, although ruminative tendencies and dysphoria levels were moderately correlated (r = .42), higher dysphoria levels predicted more errors on the goal-maintenance task; this finding indicates that rumination and dysphoria can have opposing effects on executive control. Overall, these results suggest that depressive rumination reflects a trait associated with more stability (goal maintenance) than flexibility (goal shifting).