And you have to know how to play it.
You have to know what parts of yourself and your writing take 100% concentration and effort and which don't.
Think about high school: there were probably some classes that you spent hours studying for, laboriously completing homework and sweating until you got the grade back, and other classes where you did the homework last minute, "winged" the tests, and did just fine.
As teachers, we call this "playing the game" of school. You know how many points you need to get your desired grade, you know yourself well enough to know how much effort you need to put in to achieve such grades, and you don't put in any extra effort.
It's extremely frustrating for teachers.
So why would I say writers should "play the game" of writing? Because unlike high school students, writers have a lot more on their plates than classes and homework. Like jobs that pay the bills, and families, and that car that keeps getting flats. Always do your best writing, but be aware of which areas need the most effort and concentration.
If you are great at getting that plot down on paper but have trouble setting the scene, leave working on the scene to times when you are contained and there isn't chaos going on. Don't compound your trouble. Get the plot out when your kids are playing in the next room and you're keeping an ear out for them, or in the 30 minutes it takes for the car guys to repair your tire, or when you're waiting for the pizza delivery guy because you were too busy to buy groceries and all you have in your house are canned beans and some frost-burned broccoli.
Work on setting the scene and adding descriptive details when you are alone in your calm, happy place. Work on it when you're at your writing desk, or in the chair that you never get to sit down in when your family is running all over the place, or that isn't located at the mechanics shop (darn it!). Work on setting the scene when you have that cup of tea (or cider, or vodka) at hand, music turned on low, and the mindset to be the next Ernest Hemingway, not the next Mad Hatter.
So do your best, but know your strengths and weaknesses. Don't spend all the "good" writing time working on the parts that are a breeze, and try to triage at the most difficult times for you to write.
Play the writing game to get the results you want.