One exercise book recommends that when you exercise with weights, do not show any strain on your face, but direct all your energy to lifting the weight. This makes sense in petitioning God too. It's natural for us to pray hard, wasting much energy on wondering if God has heard us or when and how he is going to respond to us. The superior and right way is to put all your energy into trusting in God and not any on feeling anxious and unsettled. In other words, pray from the heart, trust, and let it go.