I'm not aware of any studies that have been done on this, but it's a good guess that there have been some. What I'm writing here, however, isn't based on any empirical evidence, only on a hunch - supported, of course, by personal experience. It's only a personal perception. What have I learned? It seems to me that embarrassing moments are retained in memory more than those we're more proud of. I don't know how the brain works, and I certainly can't identify synapses that fire for pride differently than those that might fire for embarrassment, but I'm willing to bet that if we were to ask a random sample of people if they have a clearer picture in their minds of situations they'd like to forget than of those they happily remember, the vast majority would say yes.