Some time can be spent daydreaming but there is a lot more problem solving in fiction writing than you typically do while daydreaming. A daydream I had was that I was a gorilla playing with a baby gorilla.
If I was writing a story about this I would need to put in tension. So suddenly mommy gorilla needs to keep herself and her baby safe from poachers or leopards. Let's say that the silverback trys to help and is injured doing so. Mommy gorilla now feels guilty and scared because the troop needs a healthy mature male for defense. To help the other gorillas and herself, momma gorilla goes to find some humans that wouldn't hurt gorillas, but she is only a gorilla and, by mistake, alerts the poachers to the troop's presence.
Note, this isn't a fully worked out story but already had tension and failure that you wouldn't usually include in a daydream. To make it into a story I would obviously need a satisfying ending. To make it seem real I should obviously research gorilla habitat and gorilla poachers. I can make things up or romanticize things but I actually do need to do the research because I cannot make up the needed detail. So writing fiction, although it starts with fantasy, needs tension and problem solving that isn't usually part of daydreaming.
