Lyric discussion by colorsinvapor 

Cover art for Jet Black Heart lyrics by 5 Seconds of Summer

I think what they are saying here is that this person,author has some issues (everybody’s got their demons even wide awake or dreaming) and to protect the other person in the relationship, they decide to ''leave'', break up, let go (I’m the one who ends up leaving make it okay).

''Every fire I’ve ignited Faded to grey'' Maybe this means that this person's past relationships didn't go so well and it was their fault.

Again the person saying this probably has problems, issues with themselves and it's beginning to be a problem in the relationship (cause I’ve got a jet black heart and there’s a hurricane underneath it trying to keep us apart I write with a poison pen), but the relationship/love is what keeps them going, fighting through the problems (but these chemicals moving between us are the reason to start again)

The realtionship is falling appart and the author is trying really hard to fix it (now I'm holding on for dear life), even though they know it's not gonna go back to what it was like in the past (there's no way that we can rewind).