It fascinates me when people say they just write without planning. Their minds must work differently to mine. They must set themselves a premise and follow it through to a conclusion along a reasonably narrow path. When I set myself a premise my mind expands in all directions and presents a hundred pathways, some of which might lead to the conclusion I am looking for but others wandering off into deserts and dense bushland from which there is no return. I'm sure that is why I have started so many novels, never to finish them. They took me to place where I discovered I was lost and couldn't find my way back, My mind spawns new scenes, new characters, new ideas - so I need a way to control them - to know which are relevant to my story and which are not. The alternative for me is a chaotic kalaidoscope of imaginative ideas that don't have any real form.
I have to plan - not in intimate detail like some authors - but in broad outline. I have to know where the story is going to end because everything I write has to work towards that end. Every character must contribute, every scene. I have to have a basic structure because I have to build towards climaxes, fall away and then rebuild again.
Once I have this outline I feel comfortable, finishing each day's writing knowing where I am going to go tomorrow.