David wasn’t planning to defeat a giant that day. He just was following orders from his father. He was a sheep keeper, which didn’t involve slaying giants. He had a monotonous job that he did day after day after day. The orders David received for the day happened to lead him right into a battlefront, but he did not go looking for a giant to fight.
APPLICATION: Don’t pick fights. Don’t make mountains out of molehills. Don't be easily offended. Life has enough drama without creating more. Some people seem to find pleasure in a constant state of turmoil, and oddly enough, it's often the ones who claim to "hate drama."
As a rule, if you find yourself wanting to fight, it’s probably best for you to stay quiet. Wisdom is learning to speak out when you would rather stay quiet, and staying quiet when you’d really like to say something.