Our prayers should be about God's will being done on earth, not getting our will done in Heaven. In Phil 4:6 we read "Do not be anxious about anything, but in every situation, by prayer and petition, with thanksgiving, present your requests to God.”
We need to ask for what is good, pleasing and acceptable to God. God is not some sort of vending machine. It's not about us putting in the prayer requests to ask for certain things, and expecting necessarily that God dispenses accordingly. God is not here to give us what we don't need, and we need to be careful not to ask for those things.
If God delivers something other than what we prayed, has He answered? If we believe in Him, He gives us what's good for us, and we might be unwillingly asking for something bad, or our motives might not be pure.
Let's remember in the model prayer that Jesus taught us, "thy will be done on earth as it is in heaven". Our requests should remember this principle.
"Ask and you will receive" (Matt 7) requires us to consider all these factors. We don't have a blank check, but what we ask must be in accordance to His will. We ask and seek, and God allows us to find. Our freedom of choice leads us to God, but we must never forget He still shows the way, and our choices must conform to His will.
If we are seeking answers from God based on greed, ignorance, or selfishness, we had better hope God denies our prayers. He answers liberally when we approach Him with what we need to be pleasing to Him.