In "Portraits and Repetition", Gertrude Stein argues that repetition is better understood as "insistence":
"... there can be no repetition because the essence of that expression is insistence, and if you insist you must each time use emphasis and if you use emphasis it is not possible while anybody is alive that they should use exactly the same emphasis." (PDF)This rings true to me for basically any activity. Woodworking, cooking, dancing, guitar-playing, painting, writing, welding, negotiating, swimming, typing -- everything requires practice, and in practicing, we insist on the continued value of that activity each time. We can never repeat any performance or action exactly, by virtue of memory and time. Each repetition always means something slightly different, and changes the meaning of all the repetitions before it.
Game design theory formalizes this repetition as a "core gameplay loop" or "mechanic" or whatever, but let's keep following Stein's insistence on insistence for a minute: