This article presents a theoretical model to explain how close and caring relationships promote optimal well-being through two life contexts: coping successfully with life’s adversities and actively pursuing life opportunities for growth and development. The model highlights two relational support functions—Source of Strength (SOS) and Relational Catalyst (RC)—that are fundamental to thriving in each context. SOS support helps individuals emerge from adversity stronger or more knowledgeable, while RC support enables them to fully participate in life’s opportunities for growth and fulfillment. The model also identifies mediators that link these support functions to long-term thriving outcomes, emphasizing the importance of responsive and sensitive support behaviors. The authors argue for a broader perspective on social support, viewing it as an interpersonal process that promotes positive well-being and thriving, rather than solely buffering stress. The article concludes by providing a roadmap for future research to understand how close relationships promote or hinder thriving.This article presents a theoretical model to explain how close and caring relationships promote optimal well-being through two life contexts: coping successfully with life’s adversities and actively pursuing life opportunities for growth and development. The model highlights two relational support functions—Source of Strength (SOS) and Relational Catalyst (RC)—that are fundamental to thriving in each context. SOS support helps individuals emerge from adversity stronger or more knowledgeable, while RC support enables them to fully participate in life’s opportunities for growth and fulfillment. The model also identifies mediators that link these support functions to long-term thriving outcomes, emphasizing the importance of responsive and sensitive support behaviors. The authors argue for a broader perspective on social support, viewing it as an interpersonal process that promotes positive well-being and thriving, rather than solely buffering stress. The article concludes by providing a roadmap for future research to understand how close relationships promote or hinder thriving.