Never Be 100% Pantser or a 100% Planner

Writing Thoughts
I don’t think being 100% “pantser” is an effective way to write fiction. This method is where you have no plan and just start writing. I also believe that being a 100% planner ultimately results in analysis paralysis. (That’s where nothing gets done because you are planning too much.) Most writers I think fall into the middle, and here are 5 reasons why a bit of planning is a good thing.
Connection of points previously not thought about

When you plan you get to see the plot from a different perspective. That higher perspective can reveal recurring themes and conflicts in your work. That can help you play towards those themes, giving you book a much better impact overall.
Allows you to recognize junk to cut

Much like point one, knowing a high-level perspective can help you identify which components don’t fit. That can allow you to cut out junk the reader doesn’t need. Ultimately, the best stories are ones that are told in as few words as possible. This means that each chunk is relevant to the story, and that there is no wasted material.
Makes writing easier

Writing every day is a common desire for many writers. The biggest hurdle in this effort is not the 100th word, but the first. Just like jumping into cold water, the hardest part is that initial leap, that initial first sentence. If you have a focus or outline you can use, this makes things easier.
Allows you to “eat an elephant”

Planning a bit can also take a massive project and make it more obtainable. Few people could sit down and write an entire novel in one session. However, many people are able to take a few months and part out the topics to write. That makes it easier to complete a difficult task.
Can support being a “pantser”

This last point is the most interesting to me. Planning can help being a pantser. Knowing where to go can give you characters a default that they can ignore later. Furthermore, you can plan out systems so that no matter which choice your characters make, their journeys will increase in potency. One of the “tricks” in the Lazy Dungeon Masters Guide (which tells you how to prepare Dungeons and Dragons games with the least amount of time) is to build a list of 10 secrets. These secrets may or may not be used in every session.
I think there are a number more areas that planning can help, but this minor list should help emphasize the importance of planning. We all want a product that has as few problems as possible. These can include plot holes, incorrect pacing, grammar and more. The ultimate goal is to produce an 80% quality product as fast as possible. Why not a 99% quality product? The answer is simple: diminishing returns. To get from 20% to 50% quality could simply be fixing a major plot hole and some minor grammar mistakes. However, getting from 80% – 85% quality could mean re-writing two or three chapters to make a side character emphasize a main character’s journey. That time could be better spent writing a sequel to the endeavor with that side character in the sequel.