If God gave you what you wanted, you probably wouldn’t grow much at all, because devotion to God is not about getting, it is about seeking shelter. When you seek shelter, when you give up hope of anything else, you get God.
There may be many excellent techniques to concentrate better while chanting the Lord’s holy names, all of which are very, very good. But God is not pleased just by concentration. He is pleased by devotion. That means the character of our life.