Daydreaming is a kind of mental staging, and when a person's mind is empty of rational and perceptive matters, imagination fills it. Even the healthiest person fantasises and dreams in his mind and sometimes talks to himself. Fantasising is good, but as long as it does not cause mental problems. Daydreaming has a limit. Having a dream, or as some say, daydreaming, is one of our body's defence mechanisms, which can be useful and efficient if used properly, if daydreaming is extreme and interferes with the normal functioning of our lives, it can be destructive.