This is a repetitive prayer that you link to your breath.
On the in breath, "O Lord Jesus Christ, Son of God," on the exhale, "have mercy on me, a sinner."
After several minutes this will clear the mind of unnecessary worries.
Have you ever tried the Divine Office the Liturgy of the Hours. Here's a link to an online Church of England site:
https://www.churchofengland.org/prayer-worship/join-us-in-daily-prayer.aspx
I use this site which is roman Catholic. It is very similar but follows the calendar of our church honor saints and feasts you may not be familiar with.
http://www.ibreviary.com/m/breviario.php
I wouldn't want to corrupt you with my R.C.ways. 
but I do sense that you have a good relationship with God and desire an even greater one.
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