Next chapter, God yet again details the promise of land and descendants. (Genesis 13:14-17) Nevertheless, two chapters on, we find Abraham expecting to die childless. For a fourth time God insists he will give Abraham descendants. At last the old fossil believes. The Lord, thrilled with Abrahams refound faith, repeats his vow to give him the land. In disbelief, Abraham asks for a sign. (Genesis 15:2-8) With divine patience God dramatically shows the mighty man of faith not only his future descendants, but what will happen to them.
In the next chapter we find our faith model throwing away any hope of a miracle from God. He resorts to dubious natural means to forcibly accomplish what God seems unwilling to do. He bypasses his wife and turns to her maid for a baby. (Genesis 16:1-3)
Years later, the Lord yet again reaffirms his promise to Abraham and declares that Sarah would conceive. Abraham laughs. He is sure his wife has more potential as an Egyptian mummy than as a Hebrew one. Shes too old. Just bless Ishmael, is the crux of his reply. (Genesis 17:17-18) Yet the Lord persists. One more time our hero gropes for that slippery fish called faith.
Before long, he is again passing off Sarah as his sister, showing more faith in his powers of deception than in Gods integrity. This time it is King Abimelech who almost has a go at impregnating Sarah. (Genesis 20:2-3) Just weeks later, (assuming Genesis 18:10 to 21:2 are in chronological order) she conceived Abrahams baby.
Faith is not a non-stop flight above reality; its a fight. What distinguishes people of faith is not how rarely they hit the dirt, but how often they get up again. To be perpetually positive is impossible. The mere attempt embroils us in prayer battles and Abrahamic effort. The enemy often flees to his corner, only to prepare for the next round. You might even have climbed out of the ring, but the reward for getting back in exceeds anything anyone could offer.