This work analyzes whether there is a cognitive bias between the ideal perception of the skills and the real performance in an introductory physics class, and additionally, whether predictions of students' performance are related to various motivational variables. We examined through a validated survey and network analysis the relationship between several motivational aspects and volitional variables with the accuracy of their predictions. The results show that the students present a motivational bias when students' desires were considered, mainly in the students with low academic performance. Finally, it is necessary to explore the development of specific interventions that target the motivations of students, in order to be effective, and to reduce the gap between expected and actual grades, increasing students' metacognitive skills and thus their academic performance.