He who stands by a fire is warmed by it, and he who turns to the Lord with his mind and heart is warmed by the fervor of His love, and himself begins to return a warm disposition towards Him...The love of God is shed abroad in our hearts... (Rom. 5:5).
When despondency seizes us, let us not give in to it. Rather, fortified and protected by the light of faith, let us with great courage say to the spirit of evil: 'What are you to us, you who are cut off from God, a fugitive for Heaven, and a slave of evil? You dare not do anything to us: Christ, the Son of God, has dominion over us and over all. Leave us, you thing of bane. We are made steadfast by the uprightness of His Cross. Serpent, we trample on your head.'
We ought not to grieve or become irritated at anything because, by frequent vexation and irritability, we form the morally and physically very injurious habit of irritability, whilst by bearing opposition with equanimity we form the good and useful habit of enduring everything calmly and patiently.
If we prefer not to empty out all we possess for the love of God, let us at least not callously hold on to everything ourselves. Let us do something, then humble ourselves before God and obtain forgiveness from Him for what we have failed to do. For His love for mankind makes up for our omissions...
You ask for some way of completely eradicating irritability. The inclination to irritability is given us to use against sin, and we were never meant to use it against our fellow men. When we do, we act contrary to our true nature.