Why did Maggie Nelson write, “You’ve punctured my solitude”?

Maggie Nelson's The Argonauts is a memoir and a work of "autotheory," meaning that Nelson combines her own experiences with philosophy and theory to create not just a portrait of her own relationship and path to motherhood, but an exploration of the nature of love and family itself.
The line, "You've punctured my solitude," is a metaphor. From this line, a reader might picture solitude as a balloon or a bubble that Nelson was contained within, and the artist Harry Dodge, Nelson's partner and the antecedent of the "you" here, can be pictured as a needle puncturing the bubble and breaking through to Nelson.
This line is a quote that Nelson spoke to Harry, and she includes it in the opening pages of the book as part of her discussion of how aloof and unavailable she was before she met Harry. That completely changed once they embarked on their relationship.