Using the dual process theoretical framework (Brandtstädter & Rothermund, 2002), we examined whether the tendency to pursue goals tenaciously (TEN), in conjunction with the tendency to flexibly adjust one's preferences (FLEX), would be beneficial or detrimental for high school students' self-reported life satisfaction and achievement on tests of academic competencies. We used data from a sample of German high school students (N = 10,957) from the National Educational Panel Study (NEPS), and a combination of machine-learning-based psychometrics and latent structural equation modeling. The results showed that the interaction of TEN and FLEX was negatively associated with both outcomes of life satisfaction and test performance. Having high levels of both TEN and FLEX appear to have no benefit for students' life satisfaction and seem to be counterproductive for their achievement on competencies tests. The findings are consistent with the theory that having high levels of both TEN and FLEX would represent a regulatory dilemma in which the two tendencies work against each other. The results suggest the need for targeted interventions that build on students' personal strengths in tenacity or flexibility to minimize their regulatory dilemma of tenaciously pursuing goals while flexibly adapting them at the same time.