Adult second language acquisition takes time over an extended period of time during which the L2 motivation of learners goes through periods of ups and downs. Dörnyei, MacIntyre and Henry (2015) recognized the inherently dynamic nature of L2 motivation and called for adopting the Complex Dynamic System Theory (CDST) when studying this phenomenon. While using a CDST perspective, this mixed method study drew on Dörnyei’s (2009b) model of the Motivational Self System to examine the L2 motivation of 86 Saudi study-abroad students. Also, the construct of the Anti-ought to Self (Thompson, 2015) and aspects of the Appraisal Theory (Schumann, 2001) were adopted to guide this examination. The results of the study showed that the L2 motivation of the participants fell into four main motivational patterns. Also, some of the participants shifted into new attractor states over the course of their academic semester. Another important finding was that the Anti-ought to Self appeared as an important construct. The results of the standard multiple regressions showed that the amount of the variance in the Intended Learning Effort that was accounted for by the Anti-ought to Self alone exceeded the amount of the variance accounted for by the other explanatory variables put together. Also, the analysis of the quantitative and qualitative data showed that the use of the Appraisal Theory improved the construct validity of the Learning Experiences. The implications of these findings and future directions of the L2 motivational research were also discussed in the study.