Research has found that breakfast is associated with a more positive mood.  Some of the reasons for this include:

Several studies have shown that consuming high levels of carbohydrate is associated with better mood. As most breakfast cereals are high in carbohydrate, this offers one possible reason why eating a high carbohydrate breakfast is associated with an improved mood.

It has been shown that not only do the sensory aspects of food (such as taste) play a role in the enjoyment of food, but the appearance (colour and shape), texture, fat content, temperature and even the sound of chewing all contribute to the overall flavour perceptions of food. If you enjoy what you eat this can help lift mood.