And in the chorus, he is saying "I won't be complete without you.", "I need you.", "I miss you." or else I'll be very sad and it will feel like it's rainning everyday. (It descibes more on the chorus of the song.)
The 2nd verse is why they broke up (probably) or her parents don't approve of him. (that's why it says "I'll never be your mother's favourite, your daddy can't even look me in the eye.") And surprisingly he agrees with the parents about him, ("If I was in there shoes, I'll be doing the same thing, saying "There goes my little girl, walking through that trouble-some guy.") but then he says "But there just afraid of something they won't understand, but 'little darling' watch me change their minds." what he means is he thinks that the parents are afraid that the daughter is dating 'a bad guy that will break her heart.'But he is saying that's not true, and I'll change their minds for who they think I am, into something good. And when he says "I'll try, I'll try, I'll try, to pick up these broken pieces until I'm bleeding, if that will make you mine." he's saying I'll try really hard and try to fix everything I made, if that can make you mine again.