It was not a small call on Abram's life.
Have you ever been in a situation that required you to trust someone? To depend on another person's character and place your faith in that person? The author of the devotional recalls those trust games where you fall back and are hopefully caught by someone else. It's a good analogy, I think - to fall, trusting that you will be caught.
What makes you do it? Why would you fall, out of your own control, trusting that someone else will catch you? It's not a wise thing to do, and could result in banging into the ground. You do it, I think, because you trust the person who has promised to catch you.
Why would Abram follow God - give up his home, his life, his name - and follow? I think it must have had someone to do with his trust of God. Do we find God to be trustworthy? Will we fall and let God catch us? Isn't is a question of faith? Is that all it is?
I think it might be more than that. How do we develop that kind of trust in God? Maybe it's through remembering how many times God has caught us? Maybe it's through developing a close relationship with God and allowing God's grace to strengthen our faith? Maybe it's through stepping out, getting out of the boat, and walking?