Luke 18:1-8 (New Living Translation)
1 One day Jesus told his disciples a story to show that they should always pray and never give up. 2 “There was a judge in a certain city,” he said, “who neither feared God nor cared about people. 3 A widow of that city came to him repeatedly, saying, ‘Give me justice in this dispute with my enemy.’ 4 The judge ignored her for a while, but finally he said to himself, ‘I don’t fear God or care about people, 5 but this woman is driving me crazy. I’m going to see that she gets justice, because she is wearing me out with her constant requests!’”
6 Then the Lord said, “Learn a lesson from this unjust judge. 7 Even he rendered a just decision in the end. So don’t you think God will surely give justice to his chosen people who cry out to him day and night? Will he keep putting them off? 8 I tell you, he will grant justice to them quickly! But when the Son of Man returns, how many will he find on the earth who have faith?”
In the passage above, Jesus illustrated through a parable the importance of persistent prayer. The point here is that none of our prayers gets unanswered. We may not feel that way sometime, and there are times when we feel that God has abandoned us, but God does answer in the time that will benefit His children most.
There are circumstances that may hinder your prayers. If you are in sin and non-repentant, God will not listen to your prayers. Notice that I didn't say that He will not "hear" your prayers, because He is aware of everything, even your sinful state. If you will humble yourself, and ask Him for forgiveness, it will open up the line of communication.
What we pay for does have to be in His will for us. If we are frivolous in our prayers, or we are asking for things that are not within His plan for us, God will not gives us what we ask for. We need to always pray for wisdom and make sure we seek His will in our requests.
There are times when the answer you get is NO. Yes, we don't get everything we pray for, for God did not promise us everything when we came to Jesus. He did promise that he would meet all of our needs. In fact, as we mature in our Christian faith, we will ask for personal things much less frequently. If we focus on the needs of others and try to meet those needs, we will find that the very things we might have wanted we will get.
The New Testament talks much about prayer, and this parable is just one example. Bottom line is this, we need to pray about everything all the time, because this is how we communicate with God. Jesus extended his love to us, now it is our turn to love Him back.