Your memory rewrites itself every time you recall it

Memory is not a recording — it is a reconstruction. Each time you retrieve a memory, the brain reconsolidates it, and that process is susceptible to suggestion, emotion, and context. Elizabeth Loftus's research showed that by altering just one word in a question ('How fast were the cars going when they smashed vs. contacted?'), she could change both speed estimates and whether subjects 'remembered' broken glass that wasn't present. Eyewitness testimony is now considered unreliable by cognitive scientists, and the UK Court of Appeal takes expert evidence on memory distortion in serious cases.

Source: Loftus & Palmer, Journal of Verbal Learning and Verbal Behavior (1974)