With these words Our Lord condemns the passion of anger. Why? Because it is imperfection which can make man inclined to any sort of sin. Moreover, as St Anthony points out, man is usually blinded when overwhelmed by this passion and cannot reason properly. There are of course situations when anger is justified, for example, zealous anger for God and salvation of souls. We have examples of this kind of anger in Our Lord's life when He casts the sellers and buyers out of the temple (Matt. 21:12,13), or when St Paul rebukes Corinthians (1 Cor 4:21). There is no offence by anger justified by sin, but this anger should not result in abusive behaviour, but in meekness. It is therefore something totally different to be zealous defender of justice than behave like a mad tyrant smashing precious porcelain that cannot be repaired afterwards. Are you easy to get angry hothead? If so, then you can be irresponsible in your actions, but you are required to be watchful and at your best to control emotions in particular stressful situations. When the passion of anger try to overwhelm you, do your best to stay silent, and next day with more calm and better reasoning face the situation and gently rebuke if required by your duty. We pray: "O Lord, rebuke me not in Thy indignation, nor chastise me in thy wrath, Have mercy on me, O Lord, for I am weak" (Psalm 6:2-3). Therefore seeking mercy, be merciful to your brother, and wherever you lose control repent immediately and try to recompense in nice way those affected by your outburst. And doing this, remember Him who said: "Learn of me, because I am meek, and humble of heart, and you shall find rest to your souls." (Mt 11:29)
Image is by J-G Drouais "Jesus casts out the money-changers from the temple"