When you pray, check your ego. A product of Enlightenment rationalism and individualism, it's got a hankering for the novel, unique, and so-called “authentic." It wearies easily of praying the same thing because, frankly, it's not much interested in obedience to anything besides itself.
The ego wants to be your god, but it doesn't want you to know that. In fact, it likes that you're trying to be spiritual, to seek God, to practice the life of prayer. So long as you're trying, it can still boss you around. It can swell with pride when you're good, and knock you around when you're bad. All this only feeds the ego.
The perennial wisdom tradition in all spiritual traditions knows that humble, dogged obedience in the same direction bears the fruit of a holy life.
Modernity is quite ignorant of all that, and my ego, at least, is pretty well infected with its disease.
That's why I pray the Jesus Prayer over and over again. It's a dumb prayer. It's aim is to silence my ego who can't stand its simplicity or my dogged obedience to drawing my mind down into my heart. When my ego is brought into submission to my heart, the Center, it stands dumb before Christ.
I still can't figure out why it resists its healing.