This phenomenon endlessly fascinates me, and the degree to which this happens increases exponentially when you think back to things that happened in childhood. There are things that I vividly remember that I know didn't happen. I think it's either because I thought back and wished that certain things happened in retrospect, or whatever I "remember" was a lie or exaggeration I came up with to impress others, or maybe I simply applied my imagination and fabricated entire events in my brain.