Struggling to read these abstracts? You might be frustrated – but you also might be bored. According to our Meaning and Attentional Components (MAC) model, boredom occurs in part because mismatches between cognitive demands and resources result in attentional failure. Contradicting current theories, we present correlational and experimental evidence that this happens not only when resources exceed demands (understimulation) but also when demands exceed resources (overstimulation). A sample of 129 undergraduates were most bored when they found a simulated air traffic control task either too easy or too hard (i.e., a quadratic effect of difficulty). In contrast, difficulty and frustration were linearly related. Furthermore, in a meta-analaytic re-analysis of Westgate, Wilson, & Gilbert (2017), we found that across 6 studies and 1,276 participants, making a complex thinking task easier and less demanding made it less (not more) boring, in contrast to models of boredom as understimulation/lack of challenge. In short, people can feel bored both because something is too hard, as well as too easy. It’s the fit that matters.