Like many great actors, Emma Thompson was drawing from personal experience to inform her performance. In this case, as she told Yahoo Movies UK, she knew what it was like to have her heart broken by an unfaithful spouse. Emma Thompson was once married to actor/director Kenneth Branagh, who cheated on her with Helena Bonham Carter. So in this scene, she knew exactly how her character felt and simply had to think of her own experience to conjure the emotion necessary for the scene. It is, of course, unfortunate that Emma Thompson went through such heartbreak in her own life, but that is just one of the many ways that art imitates life, which is why this is the most real-feeling moment in a largely sugar-sweet film. It is something people can relate to, and therefore they feel Karen’s pain. You can watch the scene from Love Actually below to see the Oscar-winning actress deliver some impressive method acting.