sadness is correlated with higher spending oneself? who knew?
I don't think the study really gets into the meat of what is going on. More specific than higher spending when down, I am narrowing my discussion to retail therapy--the act of purchasing clothing/accessories to soothe oneself--and how this ties into other forms of bodily regulation.
Shopping when down occurs for the obvious reason for distracting oneself, but it is also a way to redirect self-validation. For instance, if something internal is going awry, it's easy to pretend that amping up the external will be fulfilling in some way. It is as though emotional wounds will heal if the exterior is perfect. As if looking great will make these other things disappear.
And this is how retail therapy can translate into fanatical or compulsive exercise; just replace Marc Jacobs with the gym. Instead of looking perfect in a little number, what will really make all your problems go away is washboard abs, or less fat, or tighter arms. Or whatever. But all of this is just punishment. Something is complicated and/or hurtful inside, so you better beat down the outside until you are good enough to achieve happiness.
Taken to extremes, these larger patterns can develop into body dysmorphic disorder, wherein feelings translate to literal changes in the reflection one sees of oneself. A sort of mind warp, emotions completely control the perception of self in ways that exacerbate aforementioned conditions.
Not to say that buying that great pair of shoes during a career dilemma is going to end up with BDD. In fact, there are only certain personality types that are pre-disposed or likely to develop such extreme conditions (cough, cough, perfectionists). However, the act of sprucing up the outside to compensate for the inside ties into this concept of "you are as good as you look." And no matter what you do to get yourself out of a funk, remaining aware of yourself and where your security comes from is always healthy. Plus, it is worth remembering that while a shopping spree might be fun or distracting, you need to go back and do the work to straighten out the real kinks in your life...maybe tomorrow after you have had some rest.