Hi Avril, as I’ve mentioned in some other posts, dreams have been suggested to result from brain activity during sleep. If you can, imagine the brain as a large electrochemical circuit box for a minute. When we reach certain stages of sleep (called REM sleep) the brain circuits start to replay the electrical activity they underwent during the day! It has been seen by looking at animals that learned a maze that the same circuits activated while navigating become reactivated during the animals sleep. But this activation or electrochemical activity might accidently trigger some activation in nearby circuits, so it is thought that while these circuits replay and form memories they may cause dreams by activation nearby brain regions. Perhaps really engaging some areas of the brain (for example doing the same thing all day) might make it more likely that your dream could be related to that experience, but we cannot consciously control our dreams while dreaming them.
Hope that explains a bit.
There’s no definite way of controling your dreams but their are some techniques which people can try. One area where people might want to control their dreams are people suffering from post traumatic stress or people who have recurring nightmares. One way to overcome traumatic dreams is to try and change the nightmares into “mastery dreams” where the individual still dreams of the traumatic event or nightmare but they come up with an alternative scenario which allows them to overcome that dream. Therapists encourage patients to imagine the format of the mastery dream while they’re awake and plan out the complete scenario. Then, if you consciously visualise that scenario before going to sleep sometimes that can help to influence your dreams. As Emma explained it doesn’t always work but with planning and practice sometimes we can influence what we dream.