For myself, and my ex-girlfriend, our dressing style was all about our stress levels at the time.
For her, she was in a high stress corporate situation, where you were expected to dress and act in a certain style, and at the end of the day, she just wanted to rid herself of those clothes ( and corporate style) and dress in the most comfortable (unfashionable) clothes possible. That was her release from the stress of the day, and return to normal mode.
For me, it was very similar, but opposite. I work in a male oriented, stressful manufacturing environment, and my release was to get home (early start, early finish), and slip into feminine clothing (hers), and if time allowed before my girlfriend came home, full makeup as well.
For both of us it was a stress relief, disrobing ourselves of the pressures of the day, and relaxing in a "I don't care, kind of way".