L2 (second language) grit, an essential personal resource involving perseverance of effort and consistency of interest, has been well documented via a variable-centred method. The current study employed latent profile analysis (LPA), a person-centred approach, to identify the potential profiles of L2 grit, moving beyond previous studies by recognizing student heterogeneity. Drawing on the conservation of resources (COR) theory, this study also examined the relationship between L2 grit, foreign language anxiety, and achievement within the identified profiles of L2 grit. Three profiles of L2 grit were disclosed, namely, “medium effort and interest”, “great effort but weak interest”, and “great effort and interest”. The facilitative function of foreign language anxiety on achievement was realised only for those within the “great effort and interest” profile, which was interpreted as the optimal configuration of personal resources from the lens of COR theory. This study generated insights for future studies on this topic.