We propose a computational model of emotions that takes into account two aspects of emotions: the emotions triggered by an event and the expressed emotions (the displayed ones), which may differ in real life. More particularly, we present a formalization of emotion eliciting-events based on a model of the agent's mental state composed of beliefs, choices, and uncertainties, which enables one to identify the emotional state of an agent at any time. We also introduce a fuzzy logic based model that computes facial expressions of blending for the different kinds of emotions. Finally, examples of facial expressions resulting from the implementation of our model are shown.