Decades of research have generally shown that being more rigid is associated with poorer mental health. We investigated whether all aspects of what has been termed "rigidity" are harmful. In particular, we hypothesized that the desire for simple structure (DSS) will not be associated with poor mental health, and in some cases might be associated with better mental health. In contrast, the intolerance of uncertainty (IU) was hypothesized to be associated with a wide range of indices of poor mental health. We also hypothesized that people high in IU would be less resilient in the face of stressful life events. Results across two cross-sectional surveys (N=240; N=331) supported our hypotheses. DSS was associated with less hopelessness, whereas IU was associated with more depression, anxiety, stress, suicidal ideation, and hopelessness. In addition, moderational analysis supported the hypothesis that IU magnifies the adversive effect of stressful life events on depression, anxiety and hopelessness. IU was more strongly related to the negative indices of well-being than to the positive index of life satisfaction. The implications of these findings for cognitive behavioural therapy practice are discussed.