How we change what others think, feel, believe and do
When we think of nostalgia, we may think of the 'good old days', though they may not have been that good. Indeed, nostalgia can have very negative associations and consequently be destructive for future thinking.
Though we all feel we know about nostalgia (and feeling is an important part of it), the subject can be quite complex in its experience and effect.
Nostalgia is first a recollection of something in the past. It can be a personal experience or something that is idealized, such as is found in the romanticism of classical literature. In other words, it is not necessarily memory in the traditional sense, though it can feel that way even when we hark back to times before we were born. More important than what is recalled, is the associated emotions that come with the memory or thought.
Nostalgia is often about making us feel good. It is not designed to recall what actually happened -- rather, it is about validating the past, our thoughts and our actions. We use nostalgia to make sense of our lives, validating our present thoughts and actions as well as what may have happened in the past.
A key use of nostalgia is in social bonding, connecting and reconnecting people who remember a period or event that they share in their individual histories. This is the popular game of 'do you remember when' and recounting of stories that may become more amazing with each retelling. A shared past, especially when it was emotionally significant, is a critical method of bringing people together. Armies use this to create bonds between members of platoons and regiments, for example in the way they celebrate regimental victories and conduct 'now get out of that' training, where small groups are given difficult exercises to complete together.
We are naturally optimistic about the future as this helps us take risks and make new discoveries and reach for achievements we might otherwise avoid. In the same way, we like looking back at the past with a bias that sees it in perhaps a more positive light than really happened.
Amplifying the positive
A way to make the past more positive is simply to select those things that were good and make them better. You can amplify memories in may ways, for example making the good feelings more intense, hues brighter, sounds louder, actions more heroic, friendships deeper and so on.
The reverse of amplification is to attenuate, reducing the accessibility and significance of less desirable memories. Even as we are feeling better about the good times, we conveniently avoid thinking about things that were not so nice. This is one reason why we may think of schooldays as 'the best time of life' by ignoring social struggles, bad teachers, homework, bullying, and so on.
There is a lot to be said for deleting memories that are problematic, although this is not always as easy as we may think as suppressed past events can still make a nuisance of themselves in our unconscious minds, for example as current desires are displaced into other unhelpful actions.
The simple honesty of ages past
An effect of the rose-tinted view is that we see the past as far simpler than it really was. We see pleasant times, endless warm (not hot) summers, innocent play, unquestioned friendships, and so on. Indeed, for children, their naive life can be simpler, but the realities of adulthood are not that easy. We may even hark back to romanticised previous centuries while conveniently forgetting the dangers of war, disease, inequality and other discomforts.
Outrage is a common yet destructive human emotion as righteous anger is used as a justification for vengeful and excessive attacks. Other people do things we consider contrary to all decent values. We denounce them as we become judge, jury and executioner. This makes us feel pleasantly powerful, such that feuding and even outright war can create idealized later memories as we polarize between good and evil.
In this way, terrorists and others who live by violence may use nostalgia as a motivation to restart their actions after setbacks and defeats. Even those who are less antisocial hark back to times where they were more powerful and influential, using nostalgia to fuel desires to become 'great again'.
Nostalgia can be used by recalling the past and adding emotional significance to events or periods. While the process of nostalgia is often automatic, you can also do it more deliberately, for example by amplifying good times and turning down uncomfortable memories (this can be a useful therapeutic techniques).
Nostalgia is often used in product design and advertising, for example in design of 'retro' products or producing adverts that recall a past time such as childhood or 'the sixties' when everything seems easier, nicer and more wholesome.