It's about a breakup and a guy who wants to feel like he has purpose.
The empty streets are a symbol for how the narrator reaches the girl he loves. He loves her so much he is willing to "crawl down [the streets] on hands and knees in a heartbeat" to get to her. After the breakup, however, the 'map' he had made, the way to her heart, no longer works. He can't find a way to reach her, despite that he had previously known how.
The last part of the song describes that despite him knowing she is capable of abusing his loyalty, he is willing to be manipulated if it would make her happy. He doesn't care how hard or how much he has to change. He wants to serve the girl so that he feels he has purpose.
It's about a breakup and a guy who wants to feel like he has purpose.
The empty streets are a symbol for how the narrator reaches the girl he loves. He loves her so much he is willing to "crawl down [the streets] on hands and knees in a heartbeat" to get to her. After the breakup, however, the 'map' he had made, the way to her heart, no longer works. He can't find a way to reach her, despite that he had previously known how. The last part of the song describes that despite him knowing she is capable of abusing his loyalty, he is willing to be manipulated if it would make her happy. He doesn't care how hard or how much he has to change. He wants to serve the girl so that he feels he has purpose.
[Edit: Elaboration/clarity]