Not so simple, if God is the true judger of hearts, then nothing you say or feel under your breath does not go unnoticed. What is the sense of praying if you cannot prove that your prayers work, it would be better to get up and take action and do work. Persisting in atonement , strengthens prayers to the point of true miracles. I am not judging you, just telling you how things work. Ask yourself this, would you rather have a bunch of praying for you or working for you? It would definitely depend on which people right? I never said to make your prayers public or not, but how prayers can be more effective and even cause miracles.