It cannot be understated how much kids interrupt the ability to focus on tasks. The ability to do nothing but focus on solving on a problem for a week straight felt like 100x the productivity of having to totally context switch at the end of the day to someone needing a juice or going into a screaming tantrum because the color of the cup is wrong and that being non-stop until the next work-day, which totally obliterates all the short-term working memory you had of the task at hand.

This is a good point. I’d say if having kids was the start of my mental fogginess.

Just the lack of sleep must have an large effect.

Pretty sure you mean to say, it cannot be overstated :)