Seems like the narrator was in a relationship prior to meeting Helena, and as he found her attractive he told her a couple lies that were deeper than what he felt for her, ("Don't walk away before you give me back my heart." "Sorry I've let down my guard.") , but also was not done with his previous girlfriend.
He tells her more lies in the second chorus, "You look so sweet waiting for me, while I wait for her to give me any reason to leave." He obviously thought she was sweet, but didn't care much for either of them.
He kept Helena waiting much too long and she left him, and since he never really meant what he had said to Helena, and obviously didn't care for his original girl, he left them both and proceeded to live in his erroneous way, because "guys like me never sleep alone at night" anyway.
A sort of "You're gonna leave? Okay, good, I never cared for you anyway." standpoint. A beautiful song, and unfortunately too familiar in society today. Quit being so damn greedy.