Lyric discussion by fictionalromance 

Cover art for Poison Kiss lyrics by Last Goodnight, The

Well I was going to ask Ely to make sure but I think its straightforward enough for me to get.

Basically she's saying she loves him and probably begging for him to come back but she changes her mind and the relationship is really unstable. So then he's wondering why he fell in love and how he let her fool him, then that this is the final goodbye between them. Pretty much its an on-again off-again relationship and he wants it to end.

I think it's the stress of fear that is causing his ups and downs and not her. She is no different than she ever was. Perhaps he's the one who has changed or a circumstance has/is changing and it's causing him to panic.