I never worried; I figured God knew what was in my mind and heart. I always figured prayer was for the benefit of people not God.
When I was little I remember an older brother who had nodded off to sleep during the public talk. His wife elbowed him and he thought it was time to say the prayer so he stood up and started praying right during the talk.
Another time a brother had nodded off so the brother from the platform called out his name....yup, that sleeping brother jumped up and started saying a prayer.
Another time a brother known to give long prayers, was praying away, when we all heard a snore come from the back row. A little boy had fallen asleep.