Our brains have evolved to be this way because we don't have much to gain by constantly perceiving the presence of certain smells. But, we do benefit by discovering that there are new smells around when we come across them. This way, we can identify food, be alerted to the presence of something undesirable, etc. 

This doesn't mean that something that we once encountered is permanently registered and we never register it again. In fact, all we need to do is walk out of the bakery and walk back in to register the smell of the bread again.

This sort of a behaviour is not just restricted to smells. It happens to our feelings, emotions, desires as well. 

How we feel about winning a lottery, buying something new, getting a promotion, etc are all like the aroma of the bakery that we initially experience before our brains start to ignore it. 

If we don't reset our feelings and emotions often, especially the happy ones, then we default back to normal as though these things never happened. 

Which is why gathering up more possessions or social capital or something else of the like doesn't have a lasting effect on how we feel everyday. 

When it is inevitable that we reset, why not make the most of it and consciously do the reset ourselves?