Praise be to Allah.
The issue of dealing with anger has already been discussed. Please see question no. 658. Means of dealing with anger include the following:
·Seeking refuge with Allaah from the accursed Shaytaan.
·Calming down; if you are standing, you should sit down; if you are sitting, you should lie down.
·Remembering the reward for restraining anger, as it says in the saheeh hadeeth (authentic prophetic narration): “Do not get angry and Paradise will be yours.”
·Understanding the high status of one who controls himself, as it says in the saheeh hadeeth: “Whoever restrains his anger, Allaah will cover his faults. Whoever controls his fury – even if he is able to show it – Allaah will fill his heart with hope on the Day of Resurrection.” (Classed as hasan/sound by al-Albaani in al-Silsilah al-Saheehah, 906).
·Learning what the Prophet’s (peace and blessings of Allaah be upon him) teachings are concerning anger.
·Knowing that controlling anger is one of the signs of piety, as it says in the hadeeth quoted above.
·Paying attention when reminded, controlling oneself and following advice.
·Knowing the bad effects of anger.
·Thinking about how one is affected at the moment of anger.
·Praying that Allaah will remove this resentment from one's heart.
There follows a lovely story which will help you to deal with the child whose problem you mention:
There was a boy who was always losing his temper. His father gave him a bag full of nails and said to him, “My son, I want you to hammer a nail into our garden fence every time you need to direct your anger against something and you lose your temper.”
So the son started to follow his father’s advice. On the first day he hammered in 37 nails, but getting the nails into the fence was not easy, so he started trying to control himself when he got angry. As the days went by, he was hammering in less nails, and within weeks he was able to control himself and was able to refrain from getting angry and from hammering nails. He came to his father and told him what he had achieved. His father was happy with his efforts and said to him: “But now, my son, you have to take out a nail for every day that you do not get angry.”
The son started to take out the nails for each day that he did not get angry, until there were no nails left in the fence.
He came to his father and told him what he had achieved. His father took him to the fence and said, “My son, you have done well, but look at these holes in the fence. This fence will never be the same again.” Then he added: “When you say things in a state of anger, they leave marks like these holes on the hearts of others. You can stab a person and withdraw the knife but it doesn’t matter how many times you say ‘I’m sorry,’ because the wound will remain.