In everyday confabulation and rationalisation of behaviour, agents provide sincerely believed explanations of behaviour which are ill-grounded and normally inaccurate. In this paper, I look at the commonalities and differences between confabulations and rationalisations and investigate their moral costs and benefits. Following Summers and Velleman, I argue that both can be beneficial because they constrain future behaviour through self-consistency motivations. However, I then show that the same features that make confabulations and rationalisations beneficial in some cases can also make them (...) morally costly, when behaviour is explained and justified through the endorsement of bad moral principles. I show that these effects are most likely to occur where the central element of confabulation, self-explanation, and the central element of rationalisation, self-justification, coincide. (shrink)