Well, first, the obvious:

You can't breathe a person. I mean, you could give it your best shot, but it just is not going to happen.

Second: It's usually used in a really cheesy manner, that is, it's become so over-used, that it really doesn't hold much significance at all.

Actions generally speak louder than words, but if you're hard-up for a way to express your feelings, avoid this supposedly "romantic" phrase, and use something infinitely more appealing, such as:

"Um, you have a nice eyeball, oh, if you would only let me lick your pupil, suckle your eyelids, I would be the happiest human alive!"