The Bible tells us of examples of unanswered prayers. Paul prayed three times for the "thorn in his flesh" to be removed. I don't know exactly what it was but I assume Paul thought it was a hinderance to his ministry. Here is a man that wrote the biggest part of the New Testament that prayed earnestly that a physical ailment be removed so that he could do more as a servant for Christ. It did not happen as far as we know.
Paul performed many recorded miracles but could not perform some that he wanted. He left Timothy sick and unable to travel and preach. If all prayers were answered, we would not need faith. We could or would live by answered prayers and not faith.
Two promises that hold true. God will always hear the prayer " of a broken heart and contrive spirit" and reward that prayer with eternal life. Our eternal home will be heaven given we live by faith.
The Bible says "the feverent prayer of a righteous man availeth much" It Does NOT say avileth all and everything.