Background: This study explored the physiological correlates of students' self-reported emotions in ecologically valid settings by combining biosignal data (on physical and cardiac activity) and experience sampling method (ESM) data. Aims: The aim was to examine the concurrent associations between self-reported excitement, calmness, anxiety, and boredom (adopted from the dimensional model of emotions) and students' heart rate (HR) and heart rate variability (HRV) (indicators of physiological arousal and the activation of the autonomous nervous system). Students' physical activity was controlled in the models via the metabolic equivalent of task (MET) values (actigraphy data). A second objective was to explore how to combine the information stored by these three sources of ambulatory assessment. Sample: The study comprised 136 high school students with multiple repetitive data points. Methods: For three consecutive days, students wore biometric sensors and wristbands collecting their HR, HRV, and MET signals, and answered the ESM questionnaires five times a day on smartphones. Results: When MET values were controlled for, self-reported excitement was related to higher HR as well as lower HRV during a specific moment, indicating stronger sympathetic activity (i.e., physiological arousal/activation). Self-reported boredom was related to lower HR but was unrelated to HRV. Self-reported calmness and anxiety were unrelated to HR and HRV after controlling for MET. Conclusions: A 5-min time window with a Gaussian weighted mean seemed to be an appropriate data processing method for capturing the physiological arousal (or abate) of self-reported excitement and boredom. The findings suggest that the physiological stimulus of elevated HR could be interpreted by students as an adaptive state of excitement. Combining the experience sampling approach and the physiological measures revealed how the mind and body function in interplay and can therefore provide objective evidence of emotional and motivational processes as they unfold in students' daily lives.