The Psalmist had a special relationship with his God. It seems that he knew beyond a shadow of a doubt that God would hear him when he cried out to Him.
~Psalm 3:4 I cried unto the LORD with my voice, and he heard me out of his holy hill. Selah.
Can you say this of your relationship with God? Do you absolutely know for certain that God is hearing you when you cry? If you cannot, then you are practicing religion rather than nurturing a relationship with your Heavenly Father. Think on this for a bit. A child never questions whether his father hears his cries. So stop and meditate on your relationship with God. Do you have one?