Demotivation can negatively influence the learner's attitudes and behaviors, degrade classroom group dynamics and teacher's motivation, and result in long-term and widespread negative learning outcomes. 900 university EFL learners were surveyed to investigate the demotivating factors in learning English as a foreign language (EFL) in Japan, and the relationship between past demotivating experiences and present proficiencies. Affective states and capacity to self-regulate learning were compared among learners with varying academic interests, experiences, and proficiencies. Demotivating factors were grouped into three categories: external conditions of the learning environment, internal conditions of the learner, and reactive behaviors to demotivating experiences. Internal and reactive factors were shown to correlate with long-term EFL learning outcomes. Findings from this study indicated that beginning, less-proficient learners in non-English majors were least likely to control their affective states to cope with demotivating experiences. Finally, this paper discusses steps that might prevent or minimize demotivation and facilitate remotivation. (Contains 7 tables.)