Seven Chinese EFL university students participated in a series of four online class sessions, each lasting 20 minutes. Following each session, they reviewed video recordings of their performance and rated their enjoyment and anxiety on a minute-by-minute basis. Stimulated recalls, interviews, and field notes identified factors influencing these emotional fluctuations. Results show that, in some cases, both emotions operated in a seesaw relationship, with one rising and the other falling, while in others they operated independently. A closer look reveals that the relationship between these emotions was complex and dynamic, shaped by both internal (e.g., personality) and external (e.g., task difficulty) factors. The findings also show that while EFL students initially experienced emotional turbulence at the beginning of online classes, effective emotional, pedagogical, and technological support from teachers helped learners maintain optimal emotional states over time.This work was supported by the Sichuan Cognitive Linguistics Association and is part of a project titled “Research on the Path of Cultivating the Communication Skills of Foreign Language Talents through New Quality Productivity” (#SCRY2024GJ07). It was also supported by Funding Support to GRF Proposal Rated 3.5 by the RGC (#R4233).