Genesis 12:13 Say, I pray thee, thou[ art] my sister: that it may be well with me for thy sake; and my soul shall live because of thee.
It is amazing how selfish we can be. Abraham knows that he has a beautiful wife. He is concerned that someone might want to take her from him so he asks her to say she is his sister.
That way if there is any danger it will only be for her. How often do we make decisions on how it will affect us personally without thinking of the consequences for others? How often do we live our lives for ourselves to a this same point of embarrassment? That is if anyone really knew how we felt, talked, or acted behind closed doors?