Learners' personality traits and self-assessment have an essential role in their academic achievement and the well-being of society. Although L2 grit and the core of self-assessment (CSA) have attracted considerable attention in educational research, few studies have focused on the impact of L2 grit on boosting CSA and managing foreign language anxiety (FLA). Drawing upon this existing research gap, the present study set forth to test a structural model of English as a Foreign Language (EFL) university learners' L2 grit, CSA, and FLA. The language-domain-specific grit scale (LDSGS), the core of self-assessments questionnaire (CSAQ), and the Foreign Language Classroom Anxiety Scale (FLCAS) were administered to 418 Iranian EFL university learners. The findings of structural equation modeling (SEM) reflected the contributions of L2 grit and CSA to overcoming language learners' experienced anxiety. Furthermore, the significant influence of EFL learners' CSA on FLA was concluded. The implications of the findings are to raise learners' awareness of their personality traits and self-assessment that can foster effective language instruction and assessment.