Lyric discussion by GoddessofLove 

Cover art for I'm a Ruin lyrics by Marina and the Diamonds

I love this song so much, it's definitely one of my favorite songs off of FROOT.

She's basically saying that she wants to be with this guy, but she knows that she'll just end up breaking his heart. This guy has a hard time moving on from her because he without a doubt loves her and she feels guilty because she betrayed his trust, went behind his back, and knows she doesn't deserve his love. She is telling him "I need to leave you and move on because if you let me stay with you, I'm going to just end up ruining you."