Once you pray and your prayers are not answered, you should not give up. You continue praying and asking God until He answers your prayers. The Bible says that in Him it is always yes and Amen.

Jesus says;

18 Then He spoke a parable to them, that men always ought to pray and not lose heart, 2 saying: “There was in a certain city a judge who did not fear God nor regard man. 3 Now there was a widow in that city; and she came to him, saying, ‘Get justice for me from my adversary.’ 4 And he would not for a while; but afterwards he said within himself, ‘Though I do not fear God nor regard man, 5 yet because this widow troubles me I will avenge her, lest by her continual coming she weary me.’ ”
6 Then the Lord said, “Hear what the unjust judge said. 7 And shall God not avenge His own elect who cry out day and night to Him, though He bears long with them? 8 I tell you that He will avenge them speedily. Nevertheless, when the Son of Man comes, will He really find faith on the earth?” Luke 18:1-8

If that unjust judge can think of doing well because of the persistence of someone, how much will God answer your prayers when you persist in prayers? The Bible says. Ask it will be given, seek and you will find, knock and the door will be opened. If we need anything, we just fast and pray and ask Jesus.

How can our Heavenly Father not answer when we ask, there can be a delay in answering but don’t give up. Continue asking, and that shows that you have faith in Jesus Christ, and when you persist in prayer, the answer will come at the time God has designed.
If you don’t persist, you will end up losing what God intended to give you. Ask God, who is ready to give you in abundance whatever you want. We are sustained by the Grace of God, seeking God by His word in fasting and prayer. That is the only way we can sustain in the Grace of God.