Why do we anchor our happiness to short term situational comparisons rather than large scale events? Why does our happiness seem to be most affected by recent, short term happenings rather than the high level trends of our lives?

For example, a person has begun their life in a very humble or even disadvantaged position: poor education, a lack of parental involvement, and an exposure to drug addiction. This same person, through through their own fortitude manages, to change their life trajectory so that they have a comfortable job, a home in a safe part of town, and many loving friendships. Why then, despite having overcome such odds, are they still likely to be happy or unhappy based on small, localized daily situations, like getting into a disagreement at work or having a friend cancel plans. 

To phrase the question a different way, why do large scale personal achievements often have less impact on our moment to moment satisfaction than whatever we're experiencing right now?
Research on well-being has explored happiness from different temporal perspectives. 

Much of the literature looks at how people respond to measures of life satisfaction, quality of life, and measures of tendencies to experience positive and negative emotion. These tend to reflect longer term evaluations and emotional experiences. This shows up in for example, the relatively stability that individuals show on such measures. For example Fujita and Diener (2005) examined longitudinal data over 17 years and found substantial correlations in life satisfaction over that period of time. 

There are a variety of concepts such as the hedonic treadmill and set point theory which propose that people have a general tendency when it comes to well-being. General daily experiences can lead people to deviate from their set-point, but that with the exception of a few extreme events (e.g., divorce, major trauma, etc.) people tend to return to their set point. 

That said, there is another line of research that looks more at the moment to moment affective experience. Such research has often employed experience sampling methods (e.g., Kuppens et al, 2010) and this clearly shows more of what you are talking about: i.e., the way that mood fluctuates in relation to the little daily hassles and pleasures that we experience. 

One perspective is that the global assessment and momentary moods serve different functional purposes. Momentary moods help to guide our response in particular situations. For example, a stressful situation may call for increased vigilance or attention. An experience which elicits negative emotions maybe one to avoid. In contrast, global assessments of life satisfaction are much broader and all encompassing and may help to guide us in our broader life plans.

References


Fujita, F., &amp; Diener, E. (2005). Life satisfaction set point: stability and change. Journal of personality and social psychology, 88(1), 158. PDF
Kuppens, P., Oravecz, Z., &amp; Tuerlinckx, F. (2010). Feelings change: accounting for individual differences in the temporal dynamics of affect. Journal of personality and social psychology, 99(6), 1042. PDF