“Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours.” (Mark 11:24)
Does this mean that we will get whatever we ask for if we sincerely believe that we will get it?
Not at all.
“This is the confidence we have in approaching God: that if we ask anything according to his will, he hears us.” (1 John 5:14)
"What causes fights and quarrels among you? Don’t they come from your desires that battle within you? You desire but do not have, so you kill. You covet but you cannot get what you want, so you quarrel and fight. You do not have because you do not ask God. When you ask, you do not receive, because you ask with wrong motives, that you may spend what you get on your pleasures." (James 4:1-3)
God is not interested in making his children more selfish. Do you ask for the sake of your own pleasure?
“When you ask, you do not receive, because you ask with wrong motives, that you may spend what you get on your pleasures” (James 4:3).
“But I prayed for someone I loved and they died. God let me down!”
Do you really think that is the end of the story? There is no escaping the love of God. He will make everything right in the end.
Sometimes people pray for years before receiving the thing they ask for. If it’s really important, and we really care, we’ll keep asking. God is pleased with such prayers. And in his time he will answer.
If what you’re asking for is in accordance with God’s will, you will get what you ask for. But if you are asking for something that God does not want to give, you probably won't get it. (As to why you might get it, see here.)
And if you don’t believe you are asking for something that God wants to give, why are you asking?
“But,” you might say, “if God is only giving us things that he wants to give us, why bother asking? Won’t he give us what he wants to give us anyway?”There are many things God wants to give you, but he’s waiting for you to ask. Why is he waiting for you to ask? Because he wants to give you himself. The giver is greater than the gift. You will not really appreciate a gift from him until you see that it is from him.
"No gift unrecognised as coming from God is at its own best… when in all gifts we find Him, then in Him we shall find all things." ~ George MacDonald
“Man finds it hard to get what he wants, because he does not want the best; God finds it hard to give, because He would give the best, and man will not take it.” ~ George MacDonald