"Hansei" is a Japanese word that can be loosely translated as "reflection". As an example, some Japanese parents can tell to a boy to "go to his room and do hansei" after he has been naughty.
The term has been adopted and made popular by the Lean management system. Companies do hansei. Engineers do hansei after finishing a product, or reaching (or being unable to reach) a certain goal: what went fine, what could be do better?
Perhaps, although who knows if I'm stepping into cliche land here, Eastern cultures are more prone to reflection and that's why Lean has been a natural fit for them. Hansei, in the end, can be assimilated to the Study-Adjust stages of the Shewhart cycle.
We can all use a little less of doing and a little more of reflecting about the done (I know I can). In fact, I have listened to several Lean practitioners already identify that as one of the main problems in our current world. There is no use in being wonderful at the Plan and Do stages, if we fail to study how all the planning turned out, what were the flaws and unexpected outcomes in the execution, and what will we do so that they don't reappear next time. In many social contexts, activity seems to be seen as universally a good thing. But without previous plan and further reflection, you can be actively engaged in creating a hell of a mess.
Someone even called this been centered only in Plan and Do the 'Pee pee doo doo mode'. So there goes the world.
The more places where we can apply the whole PDSA pattern, the more we learn of everything that we do, and the better we'll be at that doing that we all enjoy so much. There's a huge inertia of centuries of doing things wrong, and habits take a time to correct, but the evidence is that this way of working really works better. And if it looks slower it is only in appearance, because any gains that you obtain in the Pee Pee Doo Doo way of life evaporate quickly, and as you don't accumulate any knowledge, you are forced to reinvent the same wheel over and over and over. A good philosophy for slaves; remember what Einstein said about doing the same thing over and over?