It's really not worth all this

Two people who figured out that they shouldn't be together can still be friends, I believe. Just at a less intense level... more of a casual friendship, none of the soul-bearing, hugging stuff.
But then, just as I've become convinced, I remember his look, those eyes, that smile. How can I not react to those luminous brown eyes? Or that smile that always destroys all my carefully-crafted resolutions? How can I not react? Please tell me.
How can I possibly refrain from flashing him a giant smile when he looks my way? From bantering with him the way I used to, back in the day when I had the hope that we could be together? I don't know how NOT to flirt with him. Yikes.
I STILL have a long way to go. I can't believe this.