I found myself wanting to body-check whoever produced this pile of dreck. I haven't anything against either of the stars, they seem like decent people. However, this was a far from decent film.
I thought the premise was exploitative and the film should have been entitled "Mr. November." People would have been justifiably appalled if a film had been made about a male character who found a different woman to boff every month and then dumped her. I found myself wondering if the story was a revenge fantasy penned by a woman who had been wrongfully dumped by some cad. I also found myself feeling bad for Reeves' character and wanting to choke Theoren's. Then I found myself wanting to choke me for making the poor choice to watch this movie. Next time I want to see Keanu Reeves and Charlize Theoren together, I'll watch The Devil's Advocate, which I would give three stars.
If you want heartbreaker type romance, watch Love Story instead. Myself, I think I'll watch Bill and Ted's Excellent Adventure. I'd rather laugh than cry anytime.