Research in positive psychology, well-being, eudaimonia and happiness, and the theories of Diener, Ryff, Keyes and Seligman cover a broad range of topics including "the biological, personal, relational, institutional, cultural, and global dimensions of life".  A meta-analysis on 49 studies in 2009 showed that Positive Psychology Interventions (PPI) produced improvements in well-being and lower depression levels, the PPIs studied included writing gratitude letters, learning optimistic thinking, replaying positive life experiences and socializing with others.  In a later meta-analysis of 39 studies with 6,139 participants in 2012, the outcomes were positive. Three to six months after a PPI the effects for subjective well-being and psychological well-being were still significant. However the positive effect was weaker than in the 2009 meta analysis, the authors concluded that this was because they only used higher quality studies. The PPIs they considered included counting blessings, kindness practices, making personal goals, showing gratitude and focusing on personal strengths. 
Jane worked at home designing greeting cards, a job she used to love but now felt had become routine. Two little girls who loved to draw and paint lived next door. Eventually, Jane invited the girls in to play with all the art supplies she had. At first, she just watched, but in time she joined in. Laughing, coloring, and playing pretend with the little girls transformed Jane’s life. Not only did playing with them end her loneliness and boredom, it sparked her imagination and helped her artwork flourish. Best of all, it rekindled the playfulness and spark in Jane’s relationship with her husband.
Doses of caffeine equivalent to the amount normally found in standard servings of tea, coffee and carbonated soft drinks appear to have no diuretic action.  However, acute ingestion of caffeine in large doses (at least 250–300 mg, equivalent to the amount found in 2–3 cups of coffee or 5–8 cups of tea) results in a short-term stimulation of urine output in individuals who have been deprived of caffeine for a period of days or weeks.  This increase is due to both a diuresis (increase in water excretion) and a natriuresis (increase in saline excretion); it is mediated via proximal tubular adenosine receptor blockade.  The acute increase in urinary output may increase the risk of dehydration . However, chronic users of caffeine develop a tolerance to this effect, and experience no increase in urinary output.