The purpose of this review was to come closer to answering the question why insight gained in psychotherapy does not necessarily lead to a change in patient’s behaviour. The review of literature on the subject of insight allowed us to distinguish two types of insight: “more intellectual than emotional” (I-e) and “more emotional than intellectual” (E-i). In addition, we differentiated E-i insight with a component of negative emotions (aversive) and with a component of positive emotions (corrective). We assumed that each type of insight would motivate the patient to change their behaviour in a different way. The I-e insight makes it easier for the patient to achieve concrete adaptive goals, the E-i aversive insight discourages them from attaining maladaptive goals, while the E-i corrective insight encourages them to form and follow adaptive goals. We also analysed the influence on behaviour change of some other factors, co-occurring with insight: the therapeutic relationship, the actions of the patient and his narrative motivation. Insight does not always lead to a change in behaviour because: 1) the type of the insight does not match the type of patient’s motivation; 2) insight occurs in the context of a weak therapeutic relationship or is not reinforced by the patient’s actions; 3) insight is not a key factor of change, but rather its effect or indicator.