While I do believe there is no single path to writing a great novel (how boring would that be?) I also believe that each writer falls into one of three categories when it comes to mapping out a story. To my non-writer friends, I use the analogy that writing a book is a lot like baking a pie.
Well -- sort of.
The first group approaches writing with a tried and true recipe in front of them, following it religiously and never deviating from it. Measuring out each of the ingredients called for in the cookbook with exact precision, they trust the pie will be perfect in the end as long as they stick to the formula. They meticulously create a well-thought, near-perfect outline before ever typing a single sentence.
The second group has clear direction in their mind and knows exactly what they need to do to make a pie. They grab all the necessary ingredients and go at it, approximating how much of each to use. With confidence they employ the method I like to call "Using The Force" which relies more on feelings, senses, or even experience. Some have done it so often they just trust and do it, confident all will turn out in the end.

The third group uses a little bit of both. Although there is a general recipe to follow, most of the dialogue, prose, and imagery is improvised during the writing process. I must admit that I belong to this third group of writers who needs something down on paper to base my story on but still likes to mostly shoot from the hip.
For my last novel, I discovered that creating a "fake" family tree at ancestry.com with all my characters' names, birthdates, marriages and death dates was a necessity just so I could keep them all straight. While not the same as having a story outline, it made it much easier to steer the plot and keep the storyline believeable -- no small thing when one is writing a three-book family saga.
Does having an outline for your story make it easier to write or make you feel constrained? That is something you need to discover for yourself. The bottom line is to find the method that works best to help you produce the story you want to convey. Continuing with the pie analogy, creating and baking a dessert of quality is very time-consuming and takes a lot of effort. Others may consume it quickly without fully appreciating it, but the end result is usually delicious and you can take pride in the fact that you created it yourself.
Bon Appétit!
Which kind of writer are you? Do you follow an outline or write whatever comes to you? I'd love to get your feedback!