In his heart to forgive her
He was ready to let her go, once darkness loomed his way; not for the lack of love god forbids;
Simply because darkness would consume them both, darkness would destroy her.
But she didn't let go, she told him he still had his place in her heart, she told him he could stay and that became the core of their tragedy.
If she had let him go, it would have been much easier for both of them now.
He knows she wanted to wait, he knows she didn't mean it, she lost reign over her heart when she grew attached to Damon.
Had she let go.
He tries to understand, to make up excuses and reasons; to chastise her, to find it in his heart to accept it was normal for her to develop that attachment, but in the back of his mind there's this little ugly voice telling him of Sage, in his mind there's this small picture of Caroline battling Klaus off relentlessly without a second thought.
She chose him, however.
It should have made up for him, he should have been happy; he should have been satisfied except he was neither.
Part of her may have preferred him over Damon, but not her entire being. A fundamental part of her is with Damon.
Every interaction between her and Damon becomes a nightmare, a fire spreading through him.
Every smile, every snarky exchange, every gesture induces thousands and thousands of ideas, of doubts.
His imagination would sometimes soar wild enough to imagine them making out behind his back, making it physical.
After all, they both could, couldn't they?
He'd dismiss it; he'd say he is becoming paranoid.
He hates himself, he curses himself each day because if Damon had felt one tenth of what he is feeling now while he was with Katherine, he'd have been slaying him with a blunt knife for all those years without knowing.
Their so called relationship is falling apart; they seemingly try to mend it.
They start by reviving that sort of spark they used to share.
It works out ok at first, but on the long run it becomes another lie they are living, a lie they try to believe.
They drift apart emotionally, more and more.
She is falling out of love, only if she could see it.
He wants to tell her he will be there for her if she wants him, under any circumstances even if as pure friendship.
He wants to tell her they'd be better off as only friends now.
But she wouldn't understand that, would she?
And he is still so helplessly in love with her that he can't even hint at it in the fear she'd push him away entirely forever.
She tosses him back and forth.
She tosses Damon back and forth.
She is becoming more of the monster they were all afraid she'd turn out to be.
He resolves it is time to move on.
He decides to leave.
He tells her he found it in his heart to accept the truth, that they are done.
He found it in his heart to forgive her for straying away from him when she had promised to be wholly his.
She seemingly accepts and tells him off, tells him to go away and try to build another life.
An hour before his departure, she appears on his doorstep.
She tells him to stay in this endless loop of misery and despair.
She breaks through every line of his defences, every brick in his fortress of resolution, and for that he doesn't forgive her.