The Mood of your people must be carefully maintained. A happy populace is productive, and is likely to have breakthroughs and surges of productivity. An unhappy populace may be less productive, and in extreme circumstance can revolt or riot. The Mood of your people is determined by the actions preformed by you on your settlement. It can decrease if there is a negative food or gold production. It also decreases if you cancel trade links between villages. You can increase the mood by researching Religion or Philosophy, and by gathering Luxuries around the world.
Mood increases or decreases the production of your building. For example if your settlement is joyful; the top face of the image, then your production will be increased by 20% for that settlement. Without changing the mood of your settlement there is no way to tell if it does affect the amount of gold you get per hour.