Another way to think about money's effect on happiness is money gives an atmosphere of growth. Being able to spend more money is proof of growth.
Can money buy happiness? If yes, there's not only consumerist indulgence that can lead to happiness.
Like Gretchen Rubin, the book's author, I also very rarely feel cash register happiness. Instead, I'm usually struck by buyer's remorse when spending money. Why I'm still motivated to buy things? In this case, the author provides another explanation: money's effect can be part of the "atmosphere of growth" . Being able to spend more money to provide for loved ones or strangers, to master something new, to possess an admired object, or even just to buy organic food, is proof of growth. In this way, material growth is the evidence of spiritual growth, which is also very satisfying and can bring happiness.
One source of happiness is changing. We measure our present against the past, and we're happy if we see positive change. In a study, people were asked whether they wanted a job paid 30,000 in year one, 40,000 in year two and 50,000 in year three, or a job paid 60,000 in year one, 50,000 in year two and 40,000 in year three. In general, people preferred the first option given the fact that they would earn 30,000 more in the second option . Though their decision might seem irrational, the people who chose the first option took the importance of growth to happiness into consideration. People are very sensitive to relative changes, for better or worse.
The novelist Lisa Grunwald came up with a brilliant summation of this happiness principle: "Best is good, better is best."
 If we also consider the time value of money, choosing the second option will be even more lucrative.