The chemistry of the brain’s reward system means that when you receive a favour, like a cup of tea or a lift to work, dopamine is released, and this makes us feel good.
and the world looks quite nice all of a sudden
until you read on to this:
Random good deeds also activate our social brain, which is perked up by the idea that someone is looking out for us. Unfortunately when someone is looking out for us every day the brain doesn’t recognise this as much as it probably should.