"No, it isn't a good time. I am not going to be here."
That's it... Short and sweet..... BUT tons of information that will leave him "curious".. (which is what you want him to feel)
Let's see what his response is to that....
Let him wonder why it isn't a good time for you and let him wonder where you are going to be...
Remember.. This isn't about the "kittens"...
Remember..We HAVE to assume he is still with the OW.
You have done marvelous. Others should be LEARNING from you. Don't give away your power.
HOLD THE LINE....... There is no reason to say or do anything that may come back to haunt YOU until you know without a shadow of a doubt. Time is NOW on YOUR side....
