I would say the meaning is pretty clear on this song. He took his wife/girlfriend for granted. She did all she could and held on by loving him more than she received from him and he didn't see any of it until it was too late. After the fall of the relationship, he realized how much he loved her and how he should have told her and shown her. He always knew but his actions didn't show her. And now it's too late. She's gone. He is falling and his heartache is about the guilt of how he could have changed everything had he just said something.
I would say the meaning is pretty clear on this song. He took his wife/girlfriend for granted. She did all she could and held on by loving him more than she received from him and he didn't see any of it until it was too late. After the fall of the relationship, he realized how much he loved her and how he should have told her and shown her. He always knew but his actions didn't show her. And now it's too late. She's gone. He is falling and his heartache is about the guilt of how he could have changed everything had he just said something.