Print out the letter you posted here, and hand it to him. I think it says it quite well.

I divorced my SO after 23 years of marriage, and two wonderful kids. I didn't hate her, didn't even dislike her - just knew that there has to be more to life than what I had in my marriage. I still have nothing but respect and admiration for my former wife, and we share in raising the kids, but I think both of us are better off on our own. Just my 2 cents.