The James-Lange theory of emotion posits that emotions reflect physiological states in the body. The James-Lange theory holds that human bodies FIRST experience physical sensations, and that humans will think, act, then feel afterwards. One of the Cannon-Bard's counter-arguments to this is that one can experience an emotion simultaneously with a physical reaction and prior to an action. For instance, I see a bear holding a knife, I feel fear (and possibly bewilderment) and my body tenses up immediately, then I run away. By the time I am running away, I have definitely already felt afraid of the knife-wielding bear.

The cognitive appraisal theory holds that one's emotional experience depends on one's interpretation of the situation. This was the first theory of emotion to consider the person's appraisal of a situation, in addition to physiology and behavior.

The evolutionary theory of emotion believes that emotions developed in order to help facilitate human survival, in order to allow for reproduction. An evolutionary theory looks at emotions in the context of an evolutionary framework.

The physical muscles of the face are connected to perception of emotion, and placing one's face into a "smile" by biting a pencil can lead people to perceive happiness. The key to this question was understanding the terminology used in the question. In this case, the "physical symptoms" are actually positive, they are the muscles of the face being stimulated into the shape of a smile.

The James-Lange Theory is based on the idea that physical changes elicit emotion. William James and Carl Lange developed the theory independently, but formulated a cohesive theory. The James-Lange Theory, in its initial formation, held that if physical sensation were completely removed emotional response would also be removed. Modern theorists have since revised the theory to soften this stance, and hold rather that physical sensation significantly affects emotional response, but the relationship is not total. Support for this comes from studies of spinal cord injuries in which emotions are experienced less intensely.

In Schachter's Two-Factor Theory of emotion, the two factors are physiological arousal and cognitive label. First a person will experience a physiological sensation, and will then try to place a label on the context surrounding this response, in an effort to explain it. According to Schachter both factors are needed, and are mutually reinforcing. 

Schacter-Singer's two-factor theory of emotion poses that in order for an emotion to be considered as such, a person must experience physical arousal and be able to cognitively recognize and label this.

According to Schacter and Singer, an essential component of the way we experience emotion is the labeling of physical sensations and feelings. The way we label emotions influence how we are able to cope with them and, depending on the label, it may even prolong the emotion.

"Display rules" are norms for the expression of emotion that differ from culture to culture. Examples of display rules include neutralizing (feeling an emotion but showing no emotion), masking (feeling an emotion but showing a different emotion), and intensification (feeling an emotion but showing it more intensely than it is felt). Exaggerating is not a key term associated with display rules.

Appraisal is how we interpret events, which affects and even determines the emotions that we feel about those events. Appraisal is a cognitive process and involves explaining and evaluating how and why an event occurred the way it did. Reappraisal involves reevaluating and re-explaining the meaning of an event and it is an effective way to change the emotions associated with the event.