We rarely introduce a person merely by his or her name. We always add a description to the name to introduce the person better. For example, meet Jonathan...he is a doctor.
Similarly, when the Bible introduces Sarah, it says, hey this is Sarah. She is barren. (Genesis 11:29-30) The Bible is not being critical, it is not being insensitive, it is merely communicating what was a painfully relevant fact from that time and culture.
So when God promised Abraham and Sarah a child, it would have brought enormous joy and relief.
But when God took a full 25 years before blessing Abraham and Sarah with a child, the couple had to go through an extraordinarily difficult, painful and agonizing time of waiting.
We all spend a lot of time waiting for many, many things and more often than not, we all struggle with waiting.
It is in our waiting that the grace of God covers up and eventually heals the flaws of men.