Why does repetition(or repeated patterns) play such a large roll in ones ability to recall data(memories)?

Episodic memory refers to a capacity to remember single episodes or events because one will re-experience some aspect of the original episode. There is also "mental time travel" by Tulving which speaks of going back to that particular episode, therefore your memory creates emphasis on that particular event. Episodic memory triggers memories which can lead to a pattern in recall. Mental time travel also does this.