sometimes you are detached from reality so you admit that things weren't true later or that you think that perhaps you lied a lot in those days. so it's part of BP and it occurs often to me. The problem isn't this, but the difficulty comes from whether you were lying truly i.e. deliberately or that you thought you might have been lying in the sense that matters weren't exactly the way you thought they were, this is the illness unfortunately. it's complicated !! Many times things are invented in your mind and you realize after a day or two that what you thought that those things happened didn't in fact. Yes we invent incidents unfortunately
It can occur as part of bipolar or other psychiatric disabilities but by itself it can be a specific maladaptive behavior pattern. It depends what else is going on and what accompanies it.