The short story focuses on how we are all different people at different moments. (Quote 5) Without memory, and so without a sense of time, Earl's identity is even more fragmented than a normal person's. Earl must struggle to control the "idiots" he becomes between successive moments of insight through the use of notes and letters to himself.
In Memento, on the other hand, Leonard's personality and proactive pursuit of his goal is relatively consistent. He is still affected by emotion; in particular, during periods of stress, he is less able to retain focus on the task at hand and remember what he is doing. But, unlike Earl, he tends to shift quickly and easily between the roles of "note-taker" and "note-follower".
Primarily, Memento raises questions concerning the accuracy of memory. As Leonard tells Teddy over lunch, memory is unreliable. Memory can change small details; eye-witness testimony is not trustworthy. Instead, Leonard claims, he follows facts—photographs and established details that he has written down. As the story unfolds, however, we learn that many of Leonard's recorded "facts" have been manipulated by both himself and others. And, at the end of the film, Teddy raises the question of whether Leonard has been deceiving