In the chapter “The Argument of Comedy”, Northrop Frye writes “The tragic catharsis pass beyond moral judgement… The same is true for comic catharsis, which raises sympathy and ridicule on a moral basis, but passes beyond both.” He later adds “The ritual pattern behind the catharsis of comedy is the resurrection that follows the death, the epiphany or manifestation of the risen hero” . In other words the audience reaches a catharsis watching comedy when the hero falls and then rises to overcome the challenge. The audience can then join in a joyful relief that the hero has passed beyond the moral dilemma of the comedy.
In most romantic comedies, this state of catharsis is built into the actual structure of the genre. A couple meets, gets together, fights for a moral reason, and then make up; that’s the movie. The catharsis comes when the couple are reunited and forgive each other for the mistakes they made which separated them in the first place. In When Harry Met Sally the internal structure is changed in that most of the movie is leading them getting together for the first time but that moment of catharsis is achieved in formulaic fashion when Harry confesses his love for Sally on New Years and share a kiss. This kiss reunites Harry and Sally and acts as the moment where all is forgiven for Harry running away earlier in the movie. The moral dilemma is forgotten as the heroes kiss continues and voice over wraps up the movie. The couple become the manifestation of the risen hero and are celebrated for overcoming the moral obstacles they faced.
 Frye, Northrop. “The Argument of Comedy” in English Institute Essays 1948. (New York: Columbia, 1949) 64.