obsessionally attached, non self-aware mind-wandering with no interrupt mechanisms (Ctrl-Z for you programmers), is bad.

Task-negative cognition on the other hand, is what your brain does when there is nothing in particular it has to do; when the situation has no demanding urgencies to attend to

Here’s a law of rule-making: you are always in an existential crisis, whether or not you know it.

Our default waking mode (and also during dreaming phases of sleep) is not a brain at rest, but what is known as mind wandering.