This chapter explores Phase 4 (Nurturing the Relationship), underscoring the underestimated challenges in executing and sustaining relational contracts. This chapter stresses being prepared for continuous commitment, strategic change management, and effective governance structure design. It highlights the crucial first 6–18 months—referred to as ‘contract implementation’ or ‘transition period’—where the initial change occurs, and implementation problems can lead to delays and disruptions. Beyond this initial period continuous commitment to the relationship is essential. Two detailed case studies illustrate challenges and lessons, emphasizing the importance of onboarding for sustainable relationships and the need for a governance model aligned with objectives. Among the key takeaways, Phase 4 calls for attentive change management and onboarding processes to achieve successful relational contracts.