Lyric discussion by jumpp12 

Cover art for By Your Hand lyrics by Los Campesinos!

this song is about a guy who is generally an asshole, he treats a girl badly, uses her for sex and she falls for him, and it turns out she was probably just one of the crazy ones, it escalates to a point where he begins to get paranoid about how things are going to end and how she will react, maybe he can smell her baking a plan for revenge ("i've been dreaming you've been dreaming about me"). he doesn't want a relationship and she's really into him. the line "remember what your heart is for" is almost a plea saying "please don't take revenge on me!". like too many men he wasn't honest from the beginning and won't apologise.

My Interpretation

actually i think it could also be possible that the chorus is referring to the partner of the girl he has been sleeping with as opposed to the girl herself