Originally Posted by JinnKai

To add to the list above, ^

See her eyes? Hers. You won't get to look into them like you used to.
See that hair? Hers. Won't be able to touch and smell it like you used to.
See her body? Hers. You won't get to see that naked anymore.. touch it like you used to..
Hear her laugh? Hers. You'll not be able to hear that anymore.

..the list goes on and on, from material possession to sentimental things you love about her. Its very easy to forget all of the good qualities a woman possesses over time. Making a list of her "assets" emotionally and otherwise is a very good way to see just how much you'd be losing by cheating. That said, if you can make that list and honestly say you can give them up; then I'd advise a divorce.