No doubt you are right about what war does to you. When the Amalekites plundered all of David's and his men's camp and took not only all their possessions but also their wives and children, David must have felt pretty shattered inside, confused, weary and hopeless in that moment - especially with his own men wanting to kill him on top of the great tragedy. Scripture says:
"So David and his men came to the city, and there it was, burned with fire; and their wives, their sons, and their daughters had been taken captive. 4 Then David and the people who were with him lifted up their voices and wept, until they had no more power to weep. 5 And David’s two wives, Ahinoam the Jezreelitess, and Abigail the widow of Nabal the Carmelite, had been taken captive. 6 Now David was greatly distressed, for the people spoke of stoning him, because the soul of all the people was grieved, every man for his sons and his daughters." ." (1 Samuel 30:3-6).
Yet in this time of utter despair something remarkable is said of David: "But David strengthened himself in the Lord his God" (vs. 6). How can a person possible strengthen themself when they are fatigued from weeping, greatly distressed, and greiving? My pastor commented on this passage that "to stengthen one's self means to remind yourself of promises God has given you in the past and to stand and trust upon them in a time of trouble". I have no doubt that this is what David did here. He must have reminded himself amidst his brokeness of what God had told him sometime before, else I see no human way he could have lifted himself out of his own despair.
The same should be told to vets I think: that God can lift them out of their sorrows if they would (without denying the pain, but rather fully acknowledging it before God) surrender and entrust themselves to the God of promises and hope who gives greater things than can be conceived of on earth. God's good things are the only pathway out of utter despair.