Positive Affect:

Source: Comparing Happiness and Hypomania Risk - T. Kirkland, J. Gruber, W. A. Cunningham

"Positive affect has long been considered a hallmark of subjective happiness. Yet, high levels of positive affect have also been linked with hypomania risk: a set of cognitive, affective, and behavioral characteristics that constitute a dispositional risk for future episodes of hypomania and mania. At a personality level, two powerful predictors of affective experience are extraversion and neuroticism: extraversion has been linked to positive affect, and neuroticism to negative affect. As such, a single personality trait – extraversion – has been linked to both beneficial and harmful outcomes associated with positivity." 

"Positive affect is a general dimension of mood reflecting the extent to which people feel subjectively pleasant while being engaged with their environment. High positive affect indicates more subjective pleasure and engagement; low positive affect indicates less subjective pleasure and disengagement. For example, Watson and colleagues suggest that “high positive affect is a state of high energy, full concentration, and pleasurable engagement, whereas low positive affect is characterized by sadness and lethargy”. The temporary experience of positive affect functions as a sign that things are going well, widening the array of thoughts and actions that come to mind and facilitating approach behavior."

"A wealth of empirical work over the last three decades has demonstrated that the frequent experience of positive affect is an important component of happiness. Happiness, also referred to as subjective well-being, is a disposition defined by global positive evaluations of one’s qualities and circumstances."

"recently, some research has suggested that positive affect may not always be beneficial. This work has demonstrated that “too much” positive affect–including situationally inappropriate affect–may be linked to substantial psychological and behavioral dysfunction, such as hypomania risk: a predisposition for episodes of hypomania and mania. Mania is a core feature of bipolar disorder, a severe and recurrent clinical disorder marked by heightened and persistent disruptions in positive affectivity. Episodes of mania are temporary and occur in a small population, yet personality variables can predict risk for future manic episodes. Hypomania risk is a subclinical analogue of mania and includes a constellation of affective, cognitive, and somatic features that are associated with increased risk for the onset of mania. ... As such, positive affect in mania and hypomania risk has been characterized as “too much of a good thing” in that it reflects intense positivity that is apparently insensitive to context. Taken together, this research suggests that positive affect may be a signal of dysfunction for some individuals."

"The most basic way we understand the world is in terms of positive and negative information–reward and threat. Differences in how we respond to reward and threat may originate from differences in our baseline sensitivity. Considerable evidence suggests that extraversion and neuroticism represent the primary personality manifestations of reward and threat sensitivity, respectively. Whereas extraversion refers to reward sensitivity and the general tendency to approach, explore, and engage with novelty, neuroticism refers to punishment sensitivity and the general tendency to regulate or restrain potentially disruptive emotions and behaviors. "

"According to this revised structure, extraversion is composed of assertiveness and enthusiasm. Assertiveness reflects an orientation toward agency, drive, and social dominance (e.g., subjective potency for accomplishing goals), whereas enthusiasm denotes friendliness, sociability, and the tendency to experience positive affect. These personality aspects correspond to complementary, yet dissociable, functional strategies for interacting with positive information: motivated approach toward rewards, or “wanting,” versus enjoyment of rewards, or “liking”. “Wanting” refers specifically to incentive salience, a type of motivation that promotes approach toward and consumption of rewards, and is distinguishable from more cognitive forms of desire that involve declarative goals or explicit expectations of future outcomes. By contrast, “liking” refers specifically to the positive hedonic impact of a reward, even in the absence of conscious awareness. Because these strategies are also rooted in separate neurochemical systems (dopamine vs. opioids), they may at times become decoupled."

[Also see: Escalation and Deescalation, Mania]