It’s not necessary to particularly focus to say the prayer. You don’t need to put effort into it when you have divine love. Wherever you are,
on a stool, on a chair, in a car, anywhere, in the street, at school, in the office, at work you can say the prayer, “Lord Jesus Christ have mercy on me”, softly, without pressure, without force.
St. Porphyrios of Kaysokalivia