Living with a limited brain

Some interesting research has come out recently about the processing capacity of brains. For example, that the medial prefrontal cortex can only handle two tasks at once, or that working memory can only handle about 7 items at a time (but what's an item?), or that when people are actively trying to remember something complicated, their impulse control is reduced. In fact, there has been a lot of research showing that exerting the will to make a difficult decision uses a fuel resource (sugar from the blood) that many of these other tasks also need.

What happens when these resources are used up?  When we have been thinking too hard, or have been under heavy stress, or haven't had enough to eat or sleep, or are trying to remember too many things, or are trying to drive, or need a fix,we fall back on a simpler part of the brain. We lose the ability to think rationally, to choose future benefit over immediate reward; the ability to choose at all is reduced.  We become irritable, forgetful, angry, quick to argue.
I think one way to sell people things is to push them into this state of mental fatigue, so that they are more likely to make impulse decisions.  (Hence the TVs blaring advertisements at Walmart, or timeshare presentations.) I think it would be a good idea to plan our lives with these limitations in mind.  It can be very hard to see it happening to ourselves as it does; it just seems like everything is more irritating.  Other people see it as a bad mood.