Did you know that in Exodus the Bible says that God "hardened Pharaoh's heart"? Some think this is God "picking on Pharaoh" by making him resist Moses, but Pharaoh actually hardened his own heart 4 times prior. In other words, Pharaoh had already decided that his heart was hardened... God just stopped trying to soften him up. Callousness is a dangerous thing because it challenges God's desire to use us. What we see in the Bible are several instances of people's hearts growing callous and God simply "moving around them". God doesn't seek out the biggest, the strongest, the smartest, or the most capable... he seeks out hearts that are open to the truth that He brings.