There's...not really a good way to put it. And he's aware of how it would sound:

I wouldn't have done this under other circumstances -- only I'm not sure what circumstances happened in order to have me agree to this.

Finally, Cooper says, "I shouldn't have agreed, last night, and ordinarily I wouldn't have. Things look different this morning than they did yesterday evening. I can't explain how, or why, because I don't know. Which isn't to say that I didn't enjoy myself, because I did. Very much. But it wouldn't be a good idea to do it again."