It's so easy for many, many days to slip on whatever it is you are doing, and that, in turn, becomes overwhelming—if it's hard to keep up, it will be even harder to catch up a later point.
The same compounding effect that gets you to get lots of creative output out the door can work against you to accrue to-dos and accumulate pending work.
Drop by drop, you either fill the glass or miss it, and if you have a reference point, you'll have to go back and produce drops faster to catch up.
In short, it's way easier to ensure all drops fall inside the glass at the right moment, even if it requires an extra push of effort and willpower, as otherwise, fighting against the natural rhythm of things will make it extremely difficult.
I know, because this is what I've experienced lately, not being able to put enough time into the things I was periodically doing before.