Why do we complain of not being heard?
In the first place, we ought to be astonished by this fact: when we praise God or give him thanks for his benefits in general, we are not particularly concerned whether or not our prayer is acceptable to him. On the other hand, we demand to see the results of our petitions. What is the image of God that motivates our prayer: an instrument to be used? or the Father of our Lord Jesus Christ?
Source: Catechism of the Catholic Church (Vatican.va)