This guy fell in love with this girl, she made him happy, and then the girl just goes off once some other guy, so the singer tells the girl he's going to tell her how much he loves her, but he knows that that's going to change crap, as she's just going to go after another guy, hence, "...and watch you walk away." He knows not even explaining to her his love will make her stay.
Eh, I kind of disagree actually.
This guy fell in love with this girl, she made him happy, and then the girl just goes off once some other guy, so the singer tells the girl he's going to tell her how much he loves her, but he knows that that's going to change crap, as she's just going to go after another guy, hence, "...and watch you walk away." He knows not even explaining to her his love will make her stay.