The Prophet Muhammad (peace be upon him) told his followers: "God said: ‘Every action of the son of Adam is for him except fasting, for that is solely for Me. I give the reward for it.’ The fast is a shield. If one is fasting, he should not use foul language, raise his voice (in anger), or behave foolishly. If someone reviles him or fights with him he should say, ‘I am fasting’ (instead of responding in kind).
Fiqh-us-Sunnah, Volume 3, Number 107A
I thought this was very helpful since when you are fasting you tend to become crabby, atleast I do.