Of course we all have. It is gut wrenching. And sometimes the missing them and the heartache doesn't leave for years afterwards. If you are standing firm, and know in your heart that this is for the best, then I am thinking that you didn't want to do this, but you had no choice. You were unhappy with the life that you had with this person.
I still can't watch other people's children getting married, or a mushy love story on TV. It is very hard. Because we all remember those dreams that we all had. We remember the love that we felt, and truly hoped that it was felt towards us.
There are alot of roller coaster feelings to deal with in the next coming year...be patient with yourself. And try to look at this as a new beginning in another chapter in your life. This next one, is all about YOU. Love yourself this year, you deserve it.