It is all the game of your mind and psychology. Usually, people associate unhealthy eating habits in the morning with negative consequences such as sickness and pain. But as the afternoon passes, our mind perceives all the junk food as similar to a holiday or a rainbow. Thus, people might start the day with good intentions of staying healthy, but the willpower to resist eating unhealthy items or cake weakens as the day goes on. This was found from a research by scientists.