In Alice Munro's book "Too Much Happiness," the quote conveys a deep preoccupation with a significant person in one’s life. The individual mentioned occupies both a physical space and a prominent role in the narrator's thoughts. This dual impact suggests an intense emotional connection, making it difficult for the narrator to think of anything else when this person is present.

This statement illustrates the captivating nature of relationships, wherein someone's presence can dominate one’s thoughts, overshadowing everything else. It highlights how love or infatuation can make a person feel consumed, unable to escape the pervasive influence of another's presence on their mind and emotions.