Social interactions are crucial to affective well-being. Still, people vary interindividually and intraindividually in their social needs. Social need regulation theories state that mismatches between momentary social desire and actual social contact result in lowered affect, yet empirical knowledge about this dynamic regulation is limited. 306 participants in a sample stratified by age and gender (51% women, M_age = 39.41, range 18-80 years) answered up to 20 questionnaires about social interactions and affect while mobile sensing tracked their conversations, calls, and app usage over two days. Combining preregistered and exploratory analyses, we investigated how momentary affect relates to social dynamics, focusing on two states of mismatch between social desire and social contact: social deprivation (i.e., being alone but desiring social contact) and social oversatiation (i.e., being in contact but desiring to be alone). We used specification curve analyses to scrutinize the operationalization of these constructs. Social oversatiation was associated with decreased positive affect (PA) and increased negative affect (NA). Social deprivation, however, was unrelated to affect. Exploratory multilevel models showed that a higher desire to be alone was consistently associated with decreased affect, whereas a higher desire for social contact was related to increased affect. Mobile sensing data revealed that having more conversations was related to higher PA even when controlling for momentary social desire. Using communication apps more frequently when alone was related to higher NA. We discuss implications for social need regulation, related studies on voluntary solitude, and the advantages of combining experience sampling and mobile sensing assessments.