Someone who you don't just tell about the outer part of your life, but that you share your inner self with. Someone that you connect with throughout the week or even daily to support each other through, connect emotionally, discuss personal problems with, call on your drive home, and text message when you think of them at midnight. In my view that's not an appropriate relationship with someone of the opposite gender for someone that is married.
Agree wholeheartedly. That's for your spouse and it's playing with fire to do it with someone else. Protecting the relationship comes first, exactly what Mr. P didn't do. I asked him once why cheating had to be a part of it, if he was so miserable, why didn't he just leave me without bringing that element into it? His answer was that the sex was just a natural progression of their relationship. Which, as a married man, he had no business being in that type of relationship to begin with.