Just for a while I'd like to see how the other half live. People at school are really anti-Christian at the moment. Just for a while I'd better lay low and not say anything. Abraham thought he would leave the Promised Land for a while and go to Egypt, because being where God wanted him was too hard. Abraham's next mistake, was giving in to fear.
Fear is the enemy of love, says a well known song.
It was the enemy of Abe's love for Sarai. It is also the enemy of faith. When we give in to fear, in our eyes God seems smaller or more distant or less significant or less willing to help. Abram did not trust God to protect him from the Egyptians. At this time Egypt had just had a lot of trouble with Semitic immigrants like Abram.