I wonder how do you know that God answers your prayer and what the answer is. Does the answer come as an insight, or do you just guess it?
Just like when you ask for something from a person -- when they give it to you, you've got what you asked for. But let's say you are praying for something less tangible, like wisdom. How do you know you have received it? Perhaps it is not immediately seen, but if you asked for it with a true spiritual intention to glorify God by the "wisdom" of your dealings, it will become apparent to you that God has helped you.
At times we pray for that which is not in God's perfect will for us to have. We don't see that He answers according to what we asked for -- in fact we see He answered "No." But we can rest assured that His "no" is for our good -- and "all things work together for good to them that love God and are called according to His purposes." Rom. 8:28. We must learn to wait patiently and to trust in his perfect love to those who love Him when we cannot see His purposes. All shall work for good.