34 But David said to Saul, “Your servant used to keep sheep for his father. And when there came a lion, or a bear, and took a lamb from the flock, 35 I went after him and struck him and delivered it out of his mouth. And if he arose against me, I caught him by his beard and struck him and killed him.
(1 Sa 17:34–35).
Sadly, David's boast of killing innocent bears could very well be true. David's secret was state-of-the-art Bronze Age weaponry: the sling. Slingers were prized missile troops in the ancient world because a practiced slinger could hurl a good-sized stone (or lead) missile with incredible accuracy and lethal effect. Some lead missiles have been found with graffiti on them: "FROM ROME WITH LOVE," or the equivalent.
It is not beyond possibility that one or more shots from an expert slinger could stun a bear, making him vulnerable for clubbing. One suspects the bear usually retreated before it came to that, though. As for Goliath, he was the first person in recorded history to bring a knife to a gunfight.
St. Peter wrote: "Be sober-minded; be watchful. Your adversary the devil prowls around like a roaring lion, seeking someone to devour." (1 Pe 5:8). We need to be "watchful," just as a shepherd is watchful, and courageous and clever. Some temptations we might be able to meet head-on, but we must flee others, as Joseph fled Potiphar's wife. Prayers are the closest thing we have to sling missiles. Most importantly, the devil doesn't fight fair, and God doesn't expect us to, either. In fact, God calls the very idea, "stupid." Sometimes we must engage in a curious battle against ourselves, staying one step ahead of the world, the traitorous flesh, and the devil.
If David ever killed a bear with his bare hands, you can be sure he did not do it without God's assistance. All the saints agree that the biggest mistake we can make is to rely on ourselves.