Do you remember Achilles from study of Greek myths?
Achilles was the son of an immortal nymph named Thetis, and a mortal man named Peleus. In an effort to make Achilles invulnerable to harm, Thetis immersed Achilles in the River Styx. It worked, except for his heel, where Thetis held onto him for the baptism. Having not been exposed to the water, the heel remained vulnerable, thus our term, "Achilles Heel".
This explains, in part, Achilles heroism. He walked the Earth with very little fear of being harmed in any significant way, resulting in his noticeable embracing of danger when it arose.
As we study the book of Acts, and we specifically look at what the followers of Jesus did in order to join God in the epidemic-like growth of the church recorded there, you can't help but notice that they, too, embraced danger when it arose as they went about advancing the Kingdom.
It's almost like something in their baptism, too, allowed them to walk the Earth with very little fear of being harmed in any significant way.
In chapters 1-3, the church cruises along loving the world for Christ with very little resistance or suffering. From chapter 4 on, things change, and they experience non-stop danger. You know what they did? They just kept cruising along loving the world for Christ, considering suffering for Jesus an honor worthy of celebrating.
Do we do that? Think of all that we do - or perhaps fail to do - in the name of safety? Is it our "Achilles Heel"?
In Acts, they embraced danger in the name of Christ. They did not avoid it in the name of safety. We. Must. Do. The. Same.