I often bemoan the fact that, at times, my memory is less than perfect and have been known to insist that if given the choice, of all the cognitive abilities that exist, I would quickly choose more memory. My memory, like everyone's, has its imperfections and malfunctions and that is, in fact, the topic of Daniel Schacter's book The Seven Sins of Memory: How the Mind Forgets and Remembers. Schacter, former chair of Harvard's Psychology Department, purports that like the Seven Deadly Sins, if we can avoid committing Transience, Absent-mindedness, Blocking, Misattribution, Suggestibility, Bias, and Persistence, we would be better off. Transience (deterioration of a specific memory over time), Absent-mindedness (Where are my eyeglasses, keys, etc.) and Blocking (Tip of the tongue phenomena) are failures to recall events, facts or ideas, while Misattribution (correct memory but incorrect source), Suggestibility (recollection that is influenced by unconnected information), Bias (point of view colors recollection), and Persistence (important for long-term recall but supports Post Traumatic Stress Disorder) are failures to correctly recall information. If one is bad, then the other is worse. However, we need to be able to forget information when it is no longer useful. There are a few individuals who are able to remember every day of their lives for years. At times the information can become distracting, confusing, and troubling. There are some things we really want to forget, moments of embarrassment, hurt, and disappointment. 
What is the psychology of memory? The answer to that question will include insight of human behavior at the social and interpersonal level, as well as the neurobiology that underlies it. Check out these pictures of dendrites. Whenever we learn something, whenever we experience something, whenever we remember something, these dendrites change as a result. This does not just happen when we are developing in utero or as a growing child, but throughout our life. When dendrite growth ceases, that is suggestive of disease or death. There are a number of theories of how memory works biologically speaking. That is where we will start.
