I would say that this is a song about a guy who's social life is unraveling because of a single girl. Notice his complete indifference in the beginning when his friends are talking to him. Whether he be with this girl or only longing for her, she means so much to him and can affect him so easily that she barely needs to do anything and he is profoundly affected by it both socially, mentally, and physically. Hence, "If you want to destroy my sweater, hold this string as I walk away." Even in public this breakdown shows.

Then, later in the song, we can see his indifference toward the representation of the attractive, lonely, girl. No other girl can take his eyes or his thoughts off of the one who he is truly fixated on.

Lastly, he is telling the girl whom he is fixated on that he basically just wants to get along with her, but that it is also kind of good/satisfying in a way to see her in the same situation/agony that he has been in. Hence, "I don't want to destroy your tank-top. Let's be friends and just walk away. It's good to see you lying there in your Superman skivvies lying on the floor (lying on the floor)."

That is my take on it anyway.