It’s very common to hear inquirers or those new to Orthodoxy question the repetition in the prayers and services. I think someone has counted how many times we pray, “Lord have mercy” during Divine Liturgy but I don’t know how many that is. A lot. People wonder why we say it SO MANY TIMES. “I got it the first time!” they say. And I’ll grant you, there is a lot of repetition.
The only thing I know to compare it to is practicing scales and other finger exercises when learning to play an instrument. Most of you will know what that’s like from grim experience. It can be unbelievably boring to do them over and over and over and over… At some point you question why you have to keep doing them if you clearly know them. Of course, you’re asking the wrong question because the point of practicing scales is not to know them intellectually, but to absorb them bodily, to build muscle memory. The only way to do that is to repeat them over and over, every day.
When we pray the Jesus prayer, of course we are praying, but we’re not just repeating it to hear our own voice. Also, God doesn’t “need” to hear us say it over and over. We are the ones who need it. At first, it’s a conscious effort, “now I’m going to say the Jesus prayer.” At some point you will be walking through the grocery store and realize you’re repeating it in your head without realizing it. These times will happen more frequently over time if you persist. The ultimate goal is to be praying with every breath, every moment of our lives. The only way to get there is to do it over and over. We are creating muscle memory.