The amount of energy you have to put into a single story is limited.
Think of it like a tank of gas.
When you write, you're using up your fuel.
You can only store up so much fuel at one time, and you can only replenish a certain amount of it every day.
Guess what? Dealing with everything else in your life uses that fuel up, too.
Once you run out of the fuel, does everything stop? No.
But you begin to run on deficit. You're spending next week's fuel, and simply trying to recover will take time. It's called burnout, it happens with everything. Everyone's built differently, but most people can't keep up a maximum amount of enthusiasm about one thing for an infinite amount of time.
Its not as simple as having one type of fuel, either.
You have gold fuel, silver fuel, and low-grade fuel.
You might be able to replenish higher level fuel while using the lower grade fuel, but I cannot for example. It can also be divided even more, with different fuel types for different types of creative projects.
You might need the higher grade fuels for writing, and when you have to use the silver or low-grade fuel to write, things become very hard, quality suffers, and things won't feel right. You will struggle.
Myself, I usually can store up 30-60 days of gold fuel, and during that time I can write 5-8k words on a story i'm excited about, no problem. After that I'm using silver fuel, which doesn't feel great. I've had to do that way too much with the way I've structured my writing envrioment and plans, but I'm slowly working on improving things. I can write about 2-3k words 4-5 days a week on silver fuel. Recently I've tapped out on one story and am using low-grade fuel. Its a struggle to just write one 3k word chapter a week like that, and it feels terrible. A poor usage of time.
I'll stress that these are just the things I've found, there are no hard numbers that line up between people...you have to be mindful and think about your own experiences and think about how things are going for yourself. Then figure out your own creative 'fuel' systems work, and try to engineer a way that works well for you.
