Recently, I had a dream that I couldn’t shake, even hours into my waking day. In the dream, I learned that a close friend had been saying terrible things about me. I woke up hurt and betrayed. Even though I knew it was a dream, the emotions stuck around as if the event had actually happened.

This is a common experience. If, in a dream, you’re fighting an enemy or experiencing the joy of flying, you might eventually leave the sleeping world – but the emotions stay with you.

Most people only remember their dreams when they wake up in the morning once or twice a week, but I remember roughly four or five a week. This left me wondering: is there an impact of remembering dreams, especially the emotionally charged ones? What does it mean if you are bringing more of your dreaming life into your waking one?

What are we remembering when we remember a dream?

REM, or rapid eye movement, is the sleep phase associated with dreaming. During REM, your heart rate and blood pressure increase, your breathing becomes more irregular, and your muscles are temporarily immobilized. About 80% of people who are woken up during REM sleep will remember dreams, but when left to sleep normally, people usually forget them.

Even people with higher dream recall, like me, fail to remember the vast majority of their dreams. What we do manage to remember may be imperfect recollections. Because dreams are fragmentary and hard to remember, we can invent certain aspects of them to create a narrative, said Robert Cowan, a senior lecturer at the University of Glasgow, a philosopher who studies dreams.

“Dream reports are at least sometimes fabricated narratives that are created by the waking mind,” said Sven Bernecker, a philosopher of memory at the University of California, Irvine, and the University of Cologne. One example of this: in the 1940s and 50s, some people reported their dreams being in black and white, while today most people report dreaming in color, presumably from the introduction of color TV, he said. Their memories of their dreams were influenced by the external world, enough so to change them to Technicolor.

There has been research suggesting that differences in dream recall ability have to do with personality: that those who remember their dreams are more creative. This is largely untrue, said Michael Schredl, the scientific head of the research of the sleep laboratory in the Central Institute of Mental Health in Germany. Remembering dreams has much more to do with how much attention you give to dreams: the more attention you pay to them, the more you remember.

What do we tend to remember about dreams?

Memories of dreams can still make an impact on us. The continuity hypothesis of dreaming, first described in 1972 by psychologists Calvin Hall and Vernon Nordby, says that what happens in our dreams is connected to our waking life – desires, people, activities, emotions. This is the case even though our dreams are not limited to waking experiences, and we do things in our dreams we have never done before, like fly or accidentally forget to put on pants.

The connection to our waking lives can be thematic or emotional. In a recent study in students who study music, Schredl and his colleagues found that over half remembered dreams that were related to music. It’s also possible to compound the link between dreams and life; with second order continuity, you dream about something from your life, and then the dream in turn affects your waking life more.

Most of our dreams contain autobiographical details but when people have analyzed the content of dreams, there is very little that could be classified as episodic memories, or straightforward replays of things that happened to us. Instead, “they give us access to past mental states” or emotions and reactions we have experienced in the past, said Melanie Rosen, an assistant professor of philosophy at Trent University. For instance, you might have a dream in which you feel as anxious as you have in real life, but not about the situation that made you feel that way.

Also, even though we can remember many dull or boring things we’ve done, tedious tasks don’t tend to appear in our remembered dreams. “We don’t dream much about reading or typing on the computer,” Schredl said. Instead, dreaming focuses largely on social interactions: people and what we do with them.

Why do emotions from our dreams linger?

The philosopher René Descartes once posed a troubling question: if we don’t know when we are dreaming that we are dreaming, how can we know that we’re awake right now?

Some people, most commonly people with narcolepsy, experience dream-reality confusion, meaning they can’t tell if something happened while they were dreaming or awake. When children are very young, they also can’t always tell the difference between dreams and waking life.

For most of us, though, this is not the case. We know when we wake up from a dream that it didn’t really happen. So why did I feel hurt when I dreamed my friend had been gossiping about me? According to Rosen, when the emotional experiences from our dreams persist into waking life, it’s called the carryover effect.

Dreams are subjective experiences that happen while we are asleep, Schredl said. In a typical dream, while we are dreaming, we think we are awake. This is why they can be so affecting: the experience of dreaming is as real as your subjective experience in waking life.

“We’ve all had experiences where we remember someone who is dear to us having wronged us in our dream,” Bernecker said.

One theory is that dreams provide a kind of trial run for threatening situations. In a study of divorced women, those who dreamed more often about their ex-husbands showed better adaptation to a separation. When you have a dream your partner is cheating, it’s like asking: “What if?” The brain is probing: “How would I feel? How would I cope with this?”

Envy is “not an easy emotion to deal with in your waking life,” Schredl said. “That’s the advantage of dreams – that you can experience [it], and say, ‘How do I deal with such emotions?’”

How do our memories of dreams affect waking life?

How much your dreams affect you depends on how you regard your dreams. If you think dreams are genuine emotional experiences that represent your character, then what you do in your dreams will represent a manifestation of self. In one recent study, Schredl and his colleagues found that if people thought their nightmares represented an unconscious fear, their nightmares were more distressing. A study from 2014 found that when people have infidelity dreams, they end up fighting more with their partners.

But if you think dreams result from imagining hypotheticals, “you might think there’s more of a tenuous connection”, Cowan said.

What about when someone tells us that we have done something wrong in their dream? Bernecker believes that we should show sympathy, even if you didn’t actually do anything wrong. “By showing that [you care] about the person, you distance yourself from the image that person had of you whilst dreaming,” he said.

There are some other, more commonplace, potential side-effects. If you have a fun or exciting dream, you might start your day in a good mood: “like in waking life if you have seen a nice movie, you feel happy for another one or two hours”, Schredl said. Or if you dreamed about someone, you might reach out to them.

Rosen, who believes that our dreams are largely made up of “cognitive trash”, recently had an infidelity dream. She walked in on her partner with another woman, and he brushed it off, saying it was no big deal. When the dream ended, what she felt the most was freed from the experience. “I was so relieved to wake up,” she said.