You love your life
You love your family
You respect yourself
You respect others
You want to see your kids, grandkids, and great-grandkids play in your yard.
Smoking has a negative image, both self and public, and you're better than that.
You have control over your life, not big tobacco.
Food tastes better
Your teeth stay white
People don't make that funny face after you give them a kiss.
You realize that poisoning yourself isn't the brightest thing to do
$3650 will buy you all kinds of cool a/v toys

Most importantly, because you know you can do it.