"The beginning of anxiety is the end of faith, and the beginning of true faith is the end of anxiety." George Mueller
"You will never learn faith in comfortable surroundings. God gives us the promises in a quiet hour; God seals our covenants with great and gracious words, then He steps back and waits to see how much we believe; the He lets the tempter come, and the test seems to contradict all that He has spoken. It is then that faith wins its crown. That is the time to look up through the storm, and among the trembling, frightened seamen cry, I believe God that it shall be even as it was told me." Streams in the Desert, Jan. 4
"When you pray, believe." Mark 11:24
I read recently a quote that really hit me. "Do not pray yourself out of faith." In other words, once you have prayed for something, and know that God has confirmed it to you, you need to just simply trust. It is not wrong to continue to bring your request before God, but to continually "worry" about, and stress over, is not right. And if your prayers are making you doubt, rather than trust, then they are not the right kind of prayers.
Mark said it for us. "When you pray, believe."