Some people teach that if we pray once, that is sufficient, and any prayer beyond that one is evidence of a lack of faith. This is not in accordance with biblical teaching. Jesus instructed His disciples about prayer. The original New Testament text of His instructions used the Greek present tense which implies continuous action. Jesus told His disciples to "Ask and keep on asking, and it shall be given you; seek and keep on seeking, and you shall find; knock and keep on knocking, and the door shall be opened to you" (Luke 11:9, Amplified). This is not one prayer but continuous prayer.
Jesus told a parable about a man who was at home in bed (Luke 11:5-8). It was at midnight when he heard frantic knocking on his door. A neighbor needed some bread to feed a guest who had arrived unexpectedly. At first the man said, "I cannot get up, I will not do it." But the neighbor kept on knocking, and the householder finally walked downstairs, shoved a couple of loaves of bread out the door, and went back to bed. The man who was petitioning got his request only because of his persistence--not because he was a neighbor or a friend, but because he kept on knocking. Therefore, the concept that you must pray only once about something is clearly not biblical.
There is one exception--when God says yes. If you ask God for $1,000 and God says, "Yes, I am sending it," you should praise and thank Him for it. If you continue to ask Him, then you act as if you do not have a relationship with Him. You need to know His voice and be able to hear Him, especially when He says yes or no.