The first reason is that memory is selective. To remember an experience or event we need to pay attention to it. Then we need to rehearse it by thinking or talking about it. Events that are "encoded" in this way are "stored" in our long-term memory.
But not everything we do, say or feel everyday is encoded and stored in memory. We are more likely to encode events that stand out, are highly emotional, mark first-time experiences or represent big changes in our lives: your first ever muddy music festival or a party that got wonderfully out of control.
Recalling or "retrieving" events from our long-term memory also is motivated. By motivated we mean that remembering some events but not others serves a psychological purpose. We tend to remember events from the past that are consistent with how we want to see ourselves now. Our sense of identity and memories are completely intertwined.
Former party animals thinking about their past selectively remember party animal memories. Each time they think of these memories, instead of memories inconsistent with this picture, they reinforce a particular view of themselves and their hedonistic past.
Memory researchers call this "retrieval induced forgetting": by repeatedly rehearsing or practising some memories ("that time I partied all night"), we forget about other related memories ("that time I studied all night"), shaping and reshaping our sense of the past and ourselves.
Memories of our teenage years matter
The second reason is a phenomenon known as "the reminiscence bump". When we look back over the past, we don't remember an equal number of events across our lives. Instead, we remember more from our teenage and early adult years.
Memories in this reminiscence bump overwhelmingly are of positive, not negative, experiences. Researchers have long speculated why, but one explanation is these are the years when we form a stable lifelong identity.
Because the events that happen to us in this "bump" are formative and central to how we view ourselves, we tend to remember them well. And because - for most of us - we selectively remember the past to form a positive, optimistic identity, we encode and store positive rather than negative memories.
Interestingly, the reminiscence bump applies not just to our personal experiences, but also to the music we recognise and love. This personally significant music usually dates from our teenage and early adult years and can trigger vivid memories decades later.
So the identity we form in our early adulthood - the wild child - shapes our recollections and helps shape us for the rest of our lives - the former wild child settling down.
Memory can be a social glue
The third reason is that memory is inherently social. We use memory to build our individual identity, but just as importantly, we use memory to build social bonds, entertain others and teach the next generation ("do what I say, not what I did").
In fact, researchers have shown that adolescents who can re-tell their parents' teenage memories and connect them to their own developing sense of identity report higher levels of psychological well-being.
Over time, the exact details of what happened when we were young may become less important than the sense of belonging and shared identity we gain from joint reminiscing and storytelling.
Events become exaggerated, parties become wilder and bands become more amazing as we tell and re-tell stories for different audiences and different purposes: from nostalgic reminiscing at our high school reunion, to introducing our children to Pink Floyd, or starting those tricky parenting conversations about sex, drugs and rock 'n' roll.
So we remember and tell stories of our hedonistic past because these events were memorable, unless it was the 60s and you remember nothing! Remembering them also helps us to see ourselves then and now in desirable ways, and sharing these memories binds us to others in important ways.
But were we as wild as we remember? Perhaps or perhaps not. But our memories of more carefree times serve us well.
• This article was originally published on The Conversation. Read the original article.