Abstract Cognitive distortions are central to the conceptual and therapeutic framework of cognitive behavioural therapy (CBT), yet the existing taxonomy has remained largely unchanged since its development in the 1980s. This article proposes a novel addition to the distortions: the ‘Forever Fallacy’ defined as the tendency to project present discomforts, limitations or emotional states across imagined future timelines as if they were permanent and unchanging. Drawing on dual-process models of cognition, the Forever Fallacy is conceptualised as a heuristic, System A-driven distortion characterised by temporal fusion, stability projection and affective permanence. It differs structurally from established distortions like catastrophising or fortune telling through targeting the perceived duration and stability of anticipated future states rather than their content or likelihood. The article synthesises empirical research on affective forecasting, prospective cognition and temporal construal theory to ground the construct in established psychological science. Clinical illustrations demonstrate its presentation in anxiety, depression and existential overwhelm. Implications for case formulation are discussed alongside proposed adaptations to standard CBT interventions. Through articulating and operationalising the Forever Fallacy, this article contributes a theoretically coherent and clinically relevant extension to cognitive models of emotional distress, warranting future empirical validation and integration into therapeutic practice. Key learning aims (1) Define and use the ‘Forever Fallacy’: recognise it as the tendency to treat a current state as if it will not change, then apply it in formulation and practice by (i) naming the patient’s duration belief (‘it will always be like this’), (ii) mapping fluctuation with time-stamped ratings (for example, 0–10 every 30–60 s for 5–10 min) and (iii) running brief, time-limited behavioural tests to demonstrate change over time. (2) Differentiate the Forever Fallacy from related thinking errors by focusing on time: it fuses the present with the future, assumes things will stay the same, and treats feelings as if they will last. Unlike catastrophising or fortune-telling, it concerns duration rather than how bad something is or how likely it is to happen. (3) Use research on affective forecasting and construal level to explain why people tend to over-estimate how long and how strongly they will feel in the future and to mistake current states for fixed trajectories (Trope and Liberman, 2010; Wilson and Gilbert, 2003). (4) Apply targeted cognitive behavioural therapy (CBT) and third-wave methods that restore a sense of time; for example, episodic future simulation, thought records with time columns, and decentring, and test change across sessions (Holmes et al. , 2007; Teasdale et al. , 2002a; Yamada et al. , 2018). (5) Set the construct within familiar theory and brain science: Personal Construct Theory and Schema Therapy; the Looming Vulnerability model of anxiety; the negativity bias; and default mode network (DMN), amygdala interactions and neuroplasticity, to guide formulation and mechanism-focused intervention (Kelly, 1991; Young et al. , 2003; Riskind, 1997; Baumeister et al. , 2001; Phelps and LeDoux, 2005; Etkin et al. , 2015).
Christopher Lomas (Thu,) studied this question.