I think that this song is about a person who is in love with another person who has been through a lot emotionally and doesn't feel like they are worth anything, maybe has given up with life but the another person wants assure them that they are "loved more than you know" and that they are sorry that they couldn't defend them at the time but now they promise to that they will do better and defend them with every last breath they have so the other person never has to feel like that ever again
I think that this song is about a person who is in love with another person who has been through a lot emotionally and doesn't feel like they are worth anything, maybe has given up with life but the another person wants assure them that they are "loved more than you know" and that they are sorry that they couldn't defend them at the time but now they promise to that they will do better and defend them with every last breath they have so the other person never has to feel like that ever again