David had a very rough life ....having begun as a happy shepherd, he was thrust into a position that would rob him of much of that simplicity he had known as a boy.

For sure, he'd become frustrated ...an understatement, considering he was running to save his life.  Being frustrated, it increases the chances of making mistakes ...and when our burden is perceived as so great we feel we can't endure, then the mistake doesn't often lead to correct the mistake, but it instead just adds to the burden and to our chances of making more mistakes.