Just for practice I've been sculpting a squirrel in a basket. I thought it might come out well in a raw sort of way because I just dove in to it. Well, I soon got the basic shape but when it came to adding the needed detail like the basket weave and facial features I got into a bit of trouble. So I pulled out some ref photos and and got my squirrel, but so what?...it was just a squirrel. So I had to put the photos away again and give the squirrel the personality I wanted so it becamemy squirrel, with the personality traits I wanted.
Then there was the basket weave...it really would've helped if I'd even done a pattern like that at least once. I was also fighting the softness of the clay and the shape kept going out of round and my fingers were also mooshing the squirrel as I worked. I learned that I should have made and baked the basket first and then modeled the squirrel on it afterwards.
So I ended up baking it in the rough and I'll have loads of sanding to do to fix things. Hopefully I did just what I needed creatively at the end of the session, and will just be polishing the rough edges and not overworking it.
Anyways, the point is that you don't have to be spontaneous to be creative...creativity is just the idea, and something that needs not to be overworked, so it looks fresh. There's nothing wrong with planning out your steps ahead of time, because then the likelihood of overworking a piece has lessened, and with the end result firmly in your head you will more than likely have a fresher piece.