Psychologists still don’t understand the true function of dreaming. However, it almost certainly relates to memory, either by helping to consolidate the day’s events or enabling us to forget unwanted detail so we don’t become overloaded. In this case, recalling our dreams might not be helpful. During vivid dreaming, serotonin and noradrenaline levels are low and this might affect recall. But perhaps the main reason is that most of our waking memories make sense and are interlinked. When I try to remember what I had for breakfast today, I can link that to memories of getting up, feeding the cats and lots of other small events. But dreams are usually illogical and their events are unrelated. So when we try to recall them, we cannot follow a sensible thread and the previously vivid details just slip away.