One needn’t ruminate more than one wants or need to, suggests this study:
“The Cessation of Rumination Through Self-Affirmation,” Sander L. Koole, Karianne Smeets, Ad van Knippenberg, and Ap Dijksterhuis, Journal of Personality and Social Psychology, 1999, Vol. 77, No. 1, 111-25. The authors affirm that they are at the University of Nijmegen, The Netherlands.