But we have to understand that just because the Lord hears our prayers, doesn't mean they're always going to be answered the way we want them to be and as fast as we want them to be. Our prayers must have the bottom line of "let THY will be done." - It has to be about God's will and not our own. We cannot and should not impose our will on God.
We should always be examining our timing and we should know that God will sometimes delay. He does this to challenge our faith and allow us to modify our requests as well as to help us develop patience and endurance and trust in Him. We always need to be mindful that it's not about us - it's about God. He is not our servant - we are His and we should be patient when it comes to our prayer requests to Him.