What combination of partners' trait self-control levels produces the best relationship outcomes? The authors tested three hypotheses-complementarity (large difference in trait self-control scores), similarity (small difference in self-control scores), and totality (large sum of self-control scores)-in three diverse samples: friends, dating partners, and married couples living in the United States and the Netherlands who were tracked cross-sectionally and longitudinally. Results consistently favored the totality model: the more total self-control, the better the relationship fared. Multiple benefits were found for having mutually high self-control, including relationship satisfaction, forgiveness, secure attachment, accommodation, healthy and committed styles of loving, smooth daily interactions, absence of conflict, and absence of feeling rejected. These effects might be due to high-self-control partners' use of accommodation when there is miscommunication or problems in the relationship. Additionally, partners might "outsource" self-control to each other; hence, having a partner with higher self-control enables more outsourcing. © The Author(s) 2011.