Lyric discussion by Theotherwoman 

Cover art for Heartlines lyrics by Florence + the Machine

Just like "cosmic love" and "never let me go" and "no light" this song is about being the other woman (mistress), but in this song she is ultimately telling him to do the right thing, and fulfill his destiny with his wife. But she will always love him, she will always be able to find him by following those heart lines on his hand. It was all just a fantasy that they would ever be together in the end... but things got rocky and now it's time to let go. She tells him to think about Wednesday's up against the wall. Wednesday's were probably the days they met to have sex and be together. So always parallels water and the ocean to being is his arms (arms of the ocean) so the river she talks about in the beginning of the song is the only place she feels free