The effect of goal setting and achievement on subjective well-being was explored to test and extend the “Architecture of Sustainable Happiness” model (Lyubomirsky et al., 2005). Mediating factors, including personality were also considered to examine any individual specific effects. All participants experienced three week periods of both ‘placebo control’ and ‘goal setting.’ In addition, roughly half of the participants (N=45) completed a ‘washout’ period after their initial treatment weeks in order to demonstrate any lasting effects. Subjective well-being was found to significantly increase during the treatment weeks beyond the levels recorded by the control group. This enhancement was found to last to some extent during the washout period; although an unreliable variable prevents further explanation of the reasons for this. Positive affect displayed different patterns of change from the other subjective well-being measures throughout our investigation and recommendations for it to be considered independently are made. During the treatment weeks neuroticism was found to have a direct influence on negative affect levels. During the same period, conscientiousness was found to predict the number of goals missed, which in turn influenced the level of life satisfaction and subjective happiness. Support was provided for the beneficial influence of volitional intentional activities on subjective well-being. However the influence of personality is felt to be underestimated in Lyubomirsky et al’s model and a revision of the relative contributions to chronic levels of subjective well-being is suggested.