Although providing support in romantic relationships is important for the well-being of both partners, providing support can be effortful. People have varying implicit theories about the exertion of effort; limited willpower theorists believe that mental resources become exhausted with use, while nonlimited willpower theorists believe that exerting effort can even prepare you for future exertion. While limited willpower theorists are more likely to experience depletion and limitations themselves, they may also be more likely to perceive and empathize with the depletion and limitations of their romantic partners. We conducted a daily diary study ( N = 363; 1,429 observations) to examine how willpower theories relate to participants’ intentions to support their romantic partners in the evenings. We find that limited theorists report their partners as more tired (predicting more intention to support)—however, limited theorists also report more fatigue and lower mood themselves (predicting less intention to support). Overall, limited willpower beliefs were associated with less, not more, intent to support one’s partner for the rest of the evening. Even if limited willpower theories improve people’s abilities to perceive their partner’s fatigue, at the end of the day, they may not feel they have the mental resources to support their romantic partners.