An affair can be like a drug. And it may take more than one attempt for your W to leave it. Some people feel an emotional affair is more painful to the betrayed partner than a physical one. How you feel about that is up to you.
I understand your questioning of this as a "phase" and statistically speaking, it possibly is. Affairs generally don't lead to long term, successful relationships.
First question is, if this A continues and IF it leads to a PA... would that be a deal breaker for you? Be honest and regardless of your first answer... dig deeper and consider it again...
If you do feel that you could get over it, and TRULY forgive your W... you might stand a chance of recovering your M. It starts with you and working on yourself and fixing things in you that could have lead your W to feel she was not getting her emotional needs met, so is seeking it elsewhere.
Understand that no one will say that an A is justified. What we will say is, it really is a symptom of a deeper marital issue. And BOTH partners hold (their own personal) responsibility for the break down of the M.
If you have not, get the DR book. And read about LRT and how that will help you to get off the emotional roller coaster and do the introspective work necessary to possibly save your M.
