Is it acommon phenomenon or the excerggrated form becomes??  

i think it has something to do with the mood. for instance, every morning i feel lazy. in the afternoon i feel hyper. in the evening i feel snoozy. lol. and you have to consider the fact that we are being influenced by our environment and the people around us. if for instance there are people having a loud argument behind you, it feels irritating, right? cuz it affects us and, in turn, makes us all angry too. next time, try to observe how these outside influences can affect you. you ll notice how your mood changes.