Have you ever prayed?  Have you ever--ever at all--called out to whoever or whatever you thought or imagined was beyond you for help?  If you are human, chances are that, at some point in your life, even if it was very early in your life, you have.  Regardless of how we may feel about the existence of God, today or in our early years, we almost inevitably, when caught in an extraordinarly dire situation, tend to cry out to some idea or personnage of the divine.
     When we do so, whether or not we really believe in the reality of this "divine," we, even if we do not intend to, implicitly endorse, in some form, its existence.
     The writer of Psalm 116 understand this very well.  "I believed when I said," he wrote, "I am greatly afflicted."  The writer knew, knew implicitly that when he told God that he was in immense pain, he was, in effect, telling God that he believed he was there and, more importantly, that he was fully capable of helping him.
     So pray, pray fervently and constantly, and believe, with the writer of Psalm 116 (and the writer of the letter to the Hebrews) that, "God is, and that he responds to those who seek him" (Hebrews 11:6).
     Think about it:  if you do not believe, why would you bother to pray?