Sarah was married to Abraham. For years they were not parents but God promises that He will bless them with a child one day – that one day took vrek long to come – Sarah only fell pregnant at 90 years old – YOH!
The Bible doesn’t say much about how Sarah felt – she definitely had moments of impatience, doubt, sadness – she probably found it hard to trust God, that He would do what He said. God proves to her that He is a promise keeper in Genesis 21:1 (https://bit.ly/30F0yC0).
God has not changed. He is still true to His Word. He keeps His promises. (Psalm 18:30 – https://bit.ly/2JbVYkQ)