I try not to pray during anger spurts. (apart from a small silent prayer to remove my anger). It wouldn’t even occur to me to attempt a rosary or a chaplet in that state, so you’re miles ahead of me to begin with, since prayers should be always present in our hearts. You may find this verse of scripture helpful. Perhaps not. The connection to your question doesn’t seem obvious on the surface, but upon reflection, it seems apt to me.
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Matt 5:22 But I tell you that any man who is angry with his brother must answer for it before the court of justice, and any man who says Raca to his brother must answer for it before the Council; and any man who says to his brother, “You fool”, must answer for it in hell fire. 23 If you are bringing your gift, then, before the altar, and remember there that your brother has some ground of complaint against you, 24 leave your gift lying there before the altar, and go home; be reconciled with your brother first, and then come back to offer your gift.
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To me, it seems we should reconcile with the person who is the object of our anger, and approach the Lord with a heart of forgiveness before offering our gift, (in this case, formal prayer, such as a rosary), unless we are simply having an informal dialogue prayer with God asking for His grace in helping us to overcome feelings of anger. When we get to our protracted and focused prayer for the well being of others, we should have that intention of love firmly in our hearts.
On another note…(that is , focus and quiet in general for prayer), i.e. to have a heart of peace for prayer, and to come to meditative or contemplative state in our prayer, we need to cultivate an environment within ourselves of serenity. Serenity, like all good things, is a grace of God, and our prayers for virtue and grace are nearly always satisfied if sought sincerely.
If you practice formal prayer, such as a rosary, liturgy of the hours, divine mercy chaplet etc. ask the Lord for His peace, and for the Holy Spirit to help you to a state of internal quiet and peace at some point each day.
Having said all this, however, quiet and peace are difficult to carve out in the average day while we are enmeshed in this crazy world of 2018. Because of that, it is more important than ever to pursue those moments. We can petition God in any state. But we can only hear God’s answers in the silence.
Psalm 46:7 Nations may be in turmoil, and thrones totter, earth shrink away before his voice; 8
but the Lord of hosts is with us, the God of Jacob is our refuge. 9 Come near, and see God’s acts, his marvellous acts done on earth; 10 how he puts an end to wars all over the world, the bow shivered, the lances shattered, the shields burnt to ashes!
11 Wait quietly, and you shall have proof that I am God, claiming empire among the nations, claiming empire over the world. 12 The Lord of hosts is with us, the God of Jacob is our refuge.