Forming social relationships is an integral aspect of our lives and a topic fundamental to social psychology. Using a performance-based measure of individual differences in valence weighting, we demonstrate that the extent to which first-year college students weight positive versus negative valence when engaged in attitude generalization predicts how many peer relationships they develop during the subsequent two months (Study 1). Furthermore, we show that individuals strategically recruited for their high sensitivity to interpersonal rejection benefit from an intervention that recalibrates their valence-weighting tendencies from an overweighting of negative valence to a more balanced weighting of positive and negative valence (Study 2). Recalibration led to extended decreases in participants' rejection sensitivity and, most importantly, led them to develop more social relationships over a subsequent two-week period. These findings demonstrate that the weighting of positive versus negative valence is a fundamental process that influences complex social outcomes and that such valence weighting tendencies can be recalibrated so as to benefit individuals.