Why do some memories become hazy while others stay vivid?

I’m sure we’ve all had our share of good times and experiences that bring smiles to our faces when we recall them, but let’s (not) forget all those other wonderful moments that deserve to be in the Amnesia Hall of Fame–celebrating your 16th birthday in a convent, wearing a strapless dress two sizes too small in a high school play, and expelling gas loudly in the middle of math class (thankfully, the last thing didn’t happen to me, but it did happen to one of my classmates).

Whether good or bad, some moments may be difficult to forget while others fade or slip completely from our minds.  Depending on the person and the event, good memories are easier to remember than bad ones and vice versa.  Some make the argument that people tend to recall negative experiences better because of deep emotions that are associated with them, such as fear, but then the same can be said of positive experiences.

A number of experts believe we are wired to remember fearful and bad events so we know to avoid and protect ourselves from them in the future.  Nevertheless, if an event is so painful and traumatic, the brain will block and repress that memory as a defense mechanism. There is also the belief that we’re consciously able to expel negative memories by focusing on positive thoughts instead or by re-writing for ourselves a more acceptable narrative of what actually occurred (a.k.a. lying).

Personally, I’m a person who likes and believes in the sunny side of things.  Naturally, things haven’t always been peachy or perfect in my life, but I consciously try not to concentrate on the unpleasant memories and focus on the good ones.  That doesn’t mean I’m re-imagining or re-inventing the past; it means that I’m selecting which things I want to actively remember and which I want to slowly exit my mind.  This hasn’t always been easy to do, and many times I’m unable to do it despite my best efforts.  I often can’t help but wonder why can’t healing mental wounds be as easy as healing the physical ones?

Why, indeed.