This study explores the benefits, challenges, and factors influencing the effectiveness of HR analytics projects based on the experiences of practitioners. We conducted semi-structured interviews with 14 HR professionals and analyzed the data using iterative comparative analysis. The results show that project effectiveness includes improved work efficiency and performance, as well as changes in practitioners' perceptions and attitudes, such as through task automation and more accurate organizational diagnosis, while process difficulties were identified as cascading barriers across three stages from problem definition to insight application. Key factors influencing effectiveness were found at both the individual level (analytical and problem-solving capabilities) and the organizational level (leadership support and a data-receptive culture). Based on these findings, we propose the 'HR Analytics Execution-Learning Virtuous Cycle Model.' Finally, the study discusses academic and practical implications for the successful integration of HR analytics.