It's times like these where Damon wishes he could call Elena his. She's scared and worried as she walks down the staircase and Damon would do anything to make her seem comfortable; even if that means being her escort for the Miss MYstic Falls Ball. She walks down slowly but her breathing is heavy while scanning the room in desperation. Damon could not feel anything but love and hate as he stared. Hate; for Stefan for leaving and not being here for Elena but also love; for seeing the woman he has grown to love walk perfectly and flawlessy down the staircase. He has never been the one to abbandon a loved one, so when he walks up to Elena and takes her hand, he cannot help to let the passion for her take ahold of him. Damon has always realized Elena doesn't feel any sparks, but he can, and he feels like his whole body is on fire. He knows Elena is not Katherine. He knows that she isn 't his. He knows that she will not love him but that doesn't mean he can't care for her; like in so many ways she has done for him. She gave herself to him and Damon will always be in debt for her.
He remembers when he found out that Elena was in a car crash. Pain and true fear rose inside of him and he ran, and ran, and ran till he grew breathless. He was lost and was on the verge of breaking down till he heard her cries. Damon wanted to hold his hands to his ears to block out her pain but he didn't; the one thing that meant everything to him was hurt and needed him. So he ran and ran. He remembers the fear on her face when she saw him. He remembers how she wanted the person saving her to be Stefan, but what Damon remembers the most was Elena's soft skin and how he was lucky to have her in his arms. He watched Elena as she slept. He memorized her breathing patterns and quirked his sly smile when her eyes fluttered open. He remembers how she was dazed and confused, and how she wanted to go home. But Damon wanted at least one day with her. He wanted to show her that what he portrays to be isn't true. Damon wanted to open up to her; Damon wanted to give himself to her. So as Elena sat desperaetly at the bar and called for a beer, Damon couldn't help to laugh and talk to her. He remembers that day because Elena gave herself to him, and as always and forever, Damon will always be in debt for her.
He sits alone in his room; brooding over mindless matter while thinking about her. He knows he is going to have to leave soon. Damon can't look at Elena anymore without feeling pain and regret, so he is leaving for himself but importantly for her. She loves Stefan and deep down Damon loves his brother too. So when the time comes to leave, Damon will leave with everything of himself and a sly smile. He'll leave to keep Elena safe; He'll leave, but he will always be in debt for her love.
Because Elena gave everything of herself to Damon and Damon will always be in debt for her.