To me it seems like trashboy is upset less because she's leaving and more because her leaving makes him realise HE is the garbage person. He was so convinced by the idea that she was a terrible unlovable person that he ignored her to the point of abuse (she had no things, probably no money to spend, lived in a room not fit for living in etc.) and now that he looks properly at the situation, he realises how terrible he is; he thought he was a noble hero, instead he was an abusive husband.
Well that's what it seems like now, I'm sure it actually because "he realised his true feelings too late" bull.