Big wins or big losses are more stressful depending on your individual motivation for power. When test subjects were ranked for their power imagery interpreting stories, researchers found that strong power-types were most likely to show high cortisol levels when they experienced big losses. Among low-power folks, though, it was their big wins that caused them greater stress. They felt much better (or at least had lower cortisol levels) when the outcomes were more even or if they were the big losers.
These sorts of findings provide support for the use of reframing in attempts to encourage resiliency. Children (or adults for that matter) accustomed to interpreting events or relationships in terms of power, competition, or wins, will be the most likely to feel bodily stress in response to setbacks, disappointments, or failures. We will experience what we expect.
The scan below shows the medial frontal cortex rapidly figuring out whether it's won or lost (256 milliseconds).
Power Motivation and cortisol
Brain & Stock Market Gains and Losses
Eide Neurolearning Blog: Children More Sensitive to Negative Feedback