The focus of the present study is on two newly-born concepts in educational psychology, i.e., personal best goals (PB) and sustained flow (SF). In other words, the present study delved into English as a foreign language (EFL) students’ PB and SF by finding the most crucial sustained flows, and exploring the dynamic interplay between PB and SF in two quantitative and qualitative phases. To do so, the Persian web-based versions of the Personal Best Questionnaire (Martin, 2006) and the DMC Disposition Scale (Muir, 2016) were utilized to explore the nexus between students’ PB and SF. This is accomplished by Structural Equation Modeling (SEM) in the quantitative phase and analyzing students’ responses on open-ended items of the DMC questionnaire as the qualitative phase of the study. The results demonstrated that students’ PBs predicted their SF. The most significant cases in the qualitative phase as well as pedagogical implications and suggestions are discussed.