The shift to emergency remote teaching due to COVID-19 brought diverse psychological, emotional, and academic challenges for second language (L2) learners. Overcoming these challenges necessitated the utilization of grit, a personality trait signifying perseverance and passion to sustain academic progress. While grit and emotions have been explored in English language learning, their interaction remains underexplored in other languages. Despite Mandarin Chinese being widely learned globally, little previous work has been done to investigate learners' psychological experiences, the function of L2 grit, and the relationship between them in online learning from the perspective of positive psychology. This might lead to an incomplete understanding of this pattern across domains and contexts, thus impeding the development of this discipline. This study uses a structural equation model to analyze the relationship between L2 grit, anxiety, boredom, and enjoyment based on 204 valid responses from Chinese as a Second Language learners in mainland China. Results underscore the importance of one facet of L2 grit, perseverance of effort in online Chinese language learning, and highlight the domain-specific nature of emotions. It also suggests that educators need not be overly concerned about negative emotions in online education, as they can be overridden by positive emotions.