He could have said that for any of the following reasons :
1. To save face 2. To alleviate his own guilt 3. To test the waters (thinking it would get back to you and YOU would come RUNNING to him after hearing the news) 4. To look magnanimous
I would pay it NO MIND... you take him back when he shows REMORSE and not a MOMENT before that... LEARN to SPOT INSINCERE remorse too... he's likley to play that...
How do you detach? Get his stuff out of your life, get NEW stuff INTO your life, get new friends, new surroundings... create a new YOU and leave the OLD you to cling all she wants (ya I know that's abstract but... I think you'll get it)
With my wife I took all my belongings and put it into moving boxes (she was still living in our home when cheating) and I started some new hobbies (guitar, theatre stage hand, cycling, etc)
