Funny thread. It's tough to pick just one. I heard:
Relax. Someday we'll look back at this time and laugh that we ever had to go through this.
She's done nothing wrong, so I can't hurt her.
It's not healthy for us to share a bed anymore, because I won't have sex with two women.
And my favorite: Having my own child has become very important to me. So I'm better off with a younger woman who isn't running out of time, because there's less likelihood that I will have to pay for assisted fertility.
I could go on.... but I'll stop here. Looks like we all hear similiar statements.