I am sorry you are not my girlfriend.
I am sorry you are so hot that men melt when they see you.
I am sorry that I can't whisk you off to a romantic, secluded island and sprinkle rose petals on your bed.
You are more beautiful than words can express .......
Not too often. I mind my manners and watch my step, but if I bump into you on the street or I accidentally tip over your coffee, I will certainly apologize!