Anger is a strong feeling of displeasure or hostility. Anger is an emotion that strikes all people at one time or another. The way you react to anger, however, is more important than whether you become angry frequently. People often respond violently and uncontrollably to anger. It snatches away the wisdom of man and thus, he becomes a brute being devoid of any sense. 
Islamically, anger is a temptation and deception of Shaitân. Anger is one of the evil whispers of Shaitan, which leads to so many evils and tragedies, of which only Allah سبحانه و تعالىknows their full extent.
Anger is a secret weapon of man towards of evils but sometimes its result’s in the destruction of many noble qualities. It snatches away the wisdom of man and thus he becomes a brute beast devoid of any sense. Anger is a temptation of shaytaan and deception of shaytaan Anger is the root of all evils. Anger is a spark of fire that are always bursting. Anger is a very bad condition that weakens the person Iman (FAITH) The meaning of anger is a rage fierce, displeasure, passion excited by a sense of wrong , physical pain, inflammation, mad, hot tempered, choleric, inflamed, A violent passion excited by real or supposed injury. Anger is the strong feeling caused by extreme displeasure. Anger is a strong feeling of annoyance, displeasure and hostility.  
The good deed and the evil deed cannot be equal. Repel (the evil) with one which is better (i.e. Allâh سبحانه و تعالىordered the faithful believers to be patient at the time of anger, and to excuse those who treat them badly), then verily! he, between whom and you there was enmity, (will become) as though he was a close friend. Qur’an.Surah Fussilat 41:34
Those who spend [in Allâh's سبحانه و تعالىCause - deeds of charity, alms, etc.] in prosperity and in adversity, who repress anger, and who pardon men; verily, Allâh loves Al-Muhsinûn (the gooddoers). Qur'an.Surah Aal-'Imran 3:134
Muhammad ﷺsaid,”The strong is not the one who overcomes the people by his strenth, but the one who controls himself while in anger.” Sahih Al-Bukhari Hadith Vol 8:135 (NE 6114)
A man said to the Prophet ﷺ, "Advise me!" The Prophet ﷺsaid, "Do not become angry and furious." The man asked (the same) again and again, and the Prophet ﷺsaid in each case, "Do not become angry and furious." Sahih Al-Bukhari Hadith Vol 8:137
“Do not get angry, and Paradise will be yours.” Saheeh al-Jaami’, 7374 
Narrated Sulaiman bin Sarad رضي الله عنه: Two men abused each other in front of the Prophet ﷺwhile we were sitting with him. One of the two abused his companion furiously and his face became red. The Prophet ﷺsaid, "I know a word (sentence) the saying of which will cause him to relax if this man says it. Only if he said, 'I seek refuge with Allahسبحانه و تعالى from Satan, the outcast.
(أَعُوذُ بِاللَّهِ مِنَ الشَّيْطَانِ الرَّجِيمِ)' " Hadith - Sahih Bukhari 8.136 (NE 6115)
Narrated Abu Dharr رضي الله عنه: The Apostle of Allah ﷺsaid to us: When one of you becomes angry while standing, he should sit down. If the anger leaves him, well and good; otherwise he should lie down. Sahih Abi Dawood 4782.
1 - Seek refuge with Allah from the Devil:
Sulayman bin Sard narrated رضي الله عنه:
"I was sitting with the Prophet ﷺ, when two men began slandering one another. One of them was red in the face, and the veins on his neck were standing out. The Prophet ﷺsaid: "I know a word which, if he ﷺwere to say it, what he ﷺfeels would go away. If he ﷺsaid: "I seek refuge with Allah from the Devil," what he ﷺfeels would go away.'" 'Fath al-Bari'; 6/337.
2 - Remain silent:
The Messenger of Allah ﷺsaid: "If any of you becomes angry, let him keep silent." 'Sahih al-Jami':693
3 - Sit down or lie down:
"Abu Dharr رضي الله عنهwas taking his camels to drink at a trough that he owned, when some other people came along and said to one another: "Who can compete with Abu Dharr رضي الله عنهin bringing animals to drink and make his hair stand on end?" A man said: "I can." So, he brought his animals and competed with Abu Dharr رضي الله عنهand ended up breaking the trough. Abu Dharr رضي الله عنهwas standing when he saw this, so, he sat down, then he laid down. Someone asked him: "O Abu Dharr رضي الله عنه, why did you sit down then lie down?" He said: "The Messenger of Allah ﷺsaid: "If any of you becomes angry and he is standing, let him sit down, so that his anger will go away. If it does not go away, let him lie down.""" Reported in the 'Musnad' of Ahmad 5/152 and 'Sahih al-Jami' 694.
al-Imamal-Khattabi رحمت اللهsaid: "One who is standing is in a position to strike and destroy, while the one who is sitting is less likely to do that, and the one who is lying down can do neither. It is possible that the Prophet ﷺtold the angry person to sit down or lie down so that he would not do something that he would later regret, and Allah سبحانه و تعالىKnows best." 'Ma'alim as-Sunan'; 5/141.
4 - Smile:
Anas bin Malik رضي الله عنهnarrated: "I was walking with the Messenger of Allah ﷺ, and he was wearing a Najrani cloak with a rough collar. A bedouin came and seized him roughly by the edge of his cloak, and I saw the marks left on his neck by the collar. Then the bedouin ordered him to give him some of the wealth of Allah سبحانه و تعالىthat he had. The Prophet ﷺturned to him and smiled, then ordered that he should be given something." 'Fath al-Bari'; 10/375.
5 - Remember the advice of the Prophet ﷺ:
Abu Hurayrah رضي الله عنهnarrated:"A man said to the Prophet ﷺ: "Advise me." He said: "Do not become angry." The man repeated his request several times, and each time the Prophet ﷺsaid to him:"Do not become angry."" 'Fath al-Bari'; 10/456.
According to another narration, the man later said: "I thought about what the Prophet ﷺsaid, and I realized that anger combines all kinds of evil." Reported in the 'Musnad' of Ahmad; 5/373.