1 Samuel 25:21-22

He has paid me back evil for good. May God deal with David, be it ever so severely, if by morning I leave alive one male of all who belong to him.
1 Samuel 25: 21-22

A protracted series of trials can set us up for over-reaction.

We’ve all done it: whatever happened was just a small thing, but we snapped and said words that we wished we could take back. Maybe it had been a difficult week, or perhaps we were stressed out by our circumstances. Whatever the reason (or excuse), we over-reacted.
David has been on the run for quite a while by this point. We aren’t certain how long it’s been, but the stress has continued to build. Up to this point, he has responded well – even being willing to step away from his personal desires and submit to the Lord’s means and timing. But now Samuel has died. (25:1) David’s living link with the Lord, the man who mentored him and held him accountable, is gone. The severe and unexpected stress of this event has opened David to temptation.
So, when David asked Nabal for some material support (a reasonable request, in the light of the protection David had provided) Nabal’s refusal provoked a response completely out of proportion with David’s previous actions. After all, he hadn’t killed Saul when he had the opportunity, and Saul certainly had done far more to provoke David than had Nabal. David also hadn’t taken vengeance against those who had tried to betray him to Saul. But now, under the stress of his protracted trials and the loss of Samuel, David decided he would kill Nabal and all the males in his household.
What’s going on here? David had stepped away from the God-centered view of life that had dominated his thinking in chapter 24, and had begun to focus on himself. It was likely Samuel’s death that brought this change. We aren’t told whether David had begun to despair about the fulfillment of God’s promise, or whether, with Samuel gone, he felt it was up to him to bring about that fulfillment. Whatever he had concluded, David was focused on himself, on his reputation, on his needs, and not on the Lord. Consequently, Nabal’s insult was intolerable to David and pushed him in the direction of disaster.
This same kind of situation happens frequently. A man will bear patiently with his wife, but when one of the children or someone at work says a wrong word, he takes them off at the knees. It’s how believers end up committing adultery – feeling unloved for so long that a brief temptation brings an over-reaction. We see it illustrated elsewhere in Scripture as well: Elijah slaughters the prophets of Baal but then runs from the threats of Jezebel. Peter follows the Lord, professing his willingness to die with Him, but then panics and denies Him three times.
Satan understands this principle and will seek to use it against us whenever he can. He will throw his “change-up” pitch when we are under the greatest stress, seeking to lead us into sin. (See Matt. 4:1ff) He tempts us to sin and then, if we succumb, he accuses us of hypocrisy and faithlessness. Strangely, under the stress of the circumstances, we will often agree with him and begin to condemn ourselves. His goal is to gain leverage that will enable him to estrange us from God. But we often do his work for him by condemning ourselves, even though Scripture is clear that Christ has removed all condemnation. (Romans 8:1)
So, how do we stand against this kind of attack? How can we avoid over-reacting under stress? Our Lord’s advice to the disciples in the Garden is straight to the point: “Watch and pray so that you will not fall into temptation. The spirit is willing, but the body is weak.” (Matt. 26:41) We need to be watchful, learning the signs that indicate that we are under stress and anticipating that the enemy will try to tempt us when we are in those circumstances. When the temptation comes, we must pray that the Holy Spirit will enable us to overcome it. (Notice there’s no indication in the text that David inquired of the Lord before acting.) Then, we have to realize that although our hearts desire to obey, our physical condition can often blunt or negate that desire. Sometimes when we recognize the symptoms of stress, the best and wisest thing for us is to take time to rest and recharge – to unstress BEFORE we face temptation. When we do, we often gain the strength we need to face, and overcome, the enemy's attacks.
But we often don’t do what we know is best to do. David did none of these things, so he is headed into a disastrous situation. Thankfully, God often intervenes in such situations to keep His people from sinning. (See 1 Cor. 10:13) He has done it for us, and He is about to do it for David.