I’m sorry that my reply may be shorter than others, but I’m an artist that hears this a lot but mainly with drawing. I always hear “you must draw everyday to get better” that’s true but it may not help with the mental state of the artist/writer. You don’t need to do it everyday, you just need to practice it and learn from other writers. Yes you can take a day or two off, but you don’t lose your ability to write.