In order to have a miracle, you must first have an impossible situation. And it is important to remember that God’s promise for a miracle cannot be brought to fruition via your human plan or reasoning. You need to submit to God’s supernatural means, faith. And faith is how to obtain your miracle.
Like I said, this woman of God, Sarai made a mess out of the situation and made matters worse because she chose not to trust God by faith and came up with a reasonable solution to a supernatural promise. But God is merciful, and 13 years later, He visited her and her husband again and said that if they would listen and this time do it His way, she would bear a son within one year.