Fantasising about other people
Some people worry that fantasising about someone other than their partner is an act of betrayal, revealing either a desire to be unfaithful or that they are longer turned on by their partner alone.
In fact, this is very rarely the case. Evidence suggests that those who fantasise the most are in happy, loving, trusting relationships. It's in this kind of context that the mind explores places the body has no intention of visiting.
The benefits of fantasy
Sex generally starts in the brain. So an active imagination can mean you're ready for sex before anything physical has happened. Therefore, desire is heightened and arousal is much quicker.
Some people find an active fantasy life can add novelty to a long-standing sexual relationship. This can be particularly helpful if your partner is not as sexually adventurous as you are.
But conversely, if you find it embarrassing to experiment in bed, fantasy offers an opportunity to give your imagination free rein and to play out roles. It can be used as a practice arena where you can build confidence before embarking on something new.