We've all done it – you're walking around going about your business and suddenly you're thinking about that time in high school you said something really stupid you would never say now.
Or that time a few years ago when you made a social gaffe.
You cringe and just want to die of shame.
Why do these negative memories seem to just pop into our heads? And why do we feel so embarrassed still, when the occasion is long past?
How do memories come into our awareness?
The current thinking is there are two ways in which we recall experiences from our past.
One way is purposeful and voluntary. For example, if you try to remember what you did at work yesterday, or what you had for lunch last Saturday. This involves a deliberate and effortful process during which we search for the memory in our minds.
The second way is unintended and spontaneous. These are memories that just seem to "pop" into our minds and can even be unwanted or intrusive. So, where does this second type of memory come from?
Part of the answer lays in how memories are connected to each other. The current understanding is our past experiences are represented in connected networks of cells that reside in our brain, called neurons.
These neurons grow physical connections with each other through the overlapping information in these representations.
For example, memories might share a type of context (different beaches you've been to, restaurants you've eaten at), occur at similar periods of life (childhood, high school years), or have emotional and thematic overlap (times we have loved or argued with others).
An initial activation of a memory could be triggered by an external stimuli from the environment (sights, sounds, tastes, smells) or internal stimuli (thoughts, feelings, physical sensations).
Once neurons containing these memories are activated, associated memories are then more likely to be recalled into conscious awareness.
An example might be walking past a bakery, smelling fresh bread, and having a spontaneous thought of last weekend when you cooked a meal for a friend. This might then lead to a memory of when toast was burned and there was smoke in the house.
Not all activation will lead to a conscious memory, and at times the associations between memories might not be entirely clear to us.
Why do memories make us feel?
When memories come to mind, we often experience emotional responses to them. In fact, involuntary memories tend to be more negative than voluntary memories. Negative memories also tend to have a stronger emotional tone than positive memories.
Humans are more motivated to avoid bad outcomes, bad situations, and bad definitions of ourselves than to seek out good ones. This is likely due to the pressing need for survival in the world: physically, mentally, and socially.
So involuntary memories can make us feel acutely sad, anxious, and even ashamed of ourselves.
For example, a memory involving embarrassment or shame might indicate to us we have done something others might find to be distasteful or negative, or in some way we have violated social norms.
These emotions are important for us to feel, and we learn from our memories and these emotional responses to manage future situations differently.
Does this happen to some people more than others?
This is all well and good, and mostly we're able to remember our past and experience the emotions without too much distress. But it may happen for some people more than others, and with stronger emotions attached.
So, if you're feeling sad, well, you're more likely to recall memories related to disappointments, loss, or shame.
Feeling anxious or bad about yourself? You're more likely to recall times when you felt scared or unsure.
In some mental health disorders, such as major depression, people more often recall memories that evoke negative feelings, the negative feelings are relatively stronger, and these feelings of shame or sadness are perceived as facts about themselves. That is, feelings become facts.
Another thing that is more likely in some mental health disorders is rumination. When we ruminate, we repetitively think about negative past experiences and how we feel or felt about them.
On the surface, the function of rumination is to try and "work out" what happened and learn something or problem-solve so these experiences do not happen again.
While this is a good idea in theory, when we ruminate we become stuck in the past and re-experience negative emotions without much benefit.
Not only that, but it means those memories in our neural networks become more strongly connected with other information, and are even more likely to then be recalled involuntarily.
Can we stop the negative feelings?
The good news is memories are very adaptable. When we recall a memory we can elaborate on it and change our thoughts, feelings, and appraisals of past experiences.
In a process referred to as "reconsolidation", changes can be made so the next time that memory is recalled it is different to what it once was and has a changed emotional tone.
For example, we might remember a time when we felt anxious about a test or a job interview that didn't go so well and feel sad or ashamed.
Reflecting, elaborating, and reframing that memory might involve remembering some aspects of it that did go well, integrating it with the idea that you stepped up to a challenge even though it was hard, and reminding yourself it's okay to feel anxious or disappointed about difficult things and it does not make us a failure or a bad person.
Through this process of rewriting experiences in a way that is reasonable and self-compassionate, their prominence in our life and self-concept can be reduced, and our well-being can improve.
As for rumination, one evidenced-based strategy is to recognize when it is happening and try to shift attention onto something absorbing and sensorial (for example doing something with your hands or focusing on sights or sounds). This attention-shifting can short-circuit rumination and get you doing something more valued.
Overall, remember that even though our brain will give us little reminders of our experiences, we don't have to be stuck in the past.