Hebrews 11:11 And by faith even Sarah, who was past childbearing age, was enabled to bear children because she considered him faithful who had made the promise.
As your children grow up and leave home you are left with a longing to have them back; but that is nothing compared to the longing for a child should you not have one!
Abraham and Sarah had long past child-bearing age and yet God visited them to tell them they would soon be having a child. At first they were unbelieving but that quickly turned to faith as they waited patiently.
God will always deliver on His promises!