Similar to the four stages of cancer, marriages that end deteriorate in four distinctive and predictable stages, and once a marriage moves from stage one to two, it will ultimately die if nothing is done about it.
Are you considering trying to reconcile with your unfaithful husband? Although many women try at least once and many try several times to reconcile, you could be getting way more than you can deal with over the long run.
While it sounds nonsensical to have made the decision to leave and then feel upset, I know now that many women find themselves in this situation. I assume that often it isn't discussed because of a fear of how others will react.