"I cry aloud to the Lord; I lift up my voice to the Lord for mercy. I pour out my complaint before him; before him I tell my trouble." Psalm 142:1-2
An old saying goes, "There are only two certainties in life: death- and taxes." I'd like to name a third: trouble. Illness, broken families, stressed jobs, debt, poverty, war -the possibilities are really endless.
If you think about it, it is understandable. For what would it take to make and keep anyone permanently, completely happy? Perfect childhood, health, looks, family, friends, colleagues, job (or no work at all!)? In a fallible world where we humans are so bound up together, and dependent upon each other, and yet retain our free will, it is only a wonder that there aren't more riots on the streets!
So the psalmist, David, does not wear himself out with wondering why trouble should have come to him in the first place. He accepts it as part of life. In his case he is being chased across an arid wilderness by King Saul and his soldiers, and is hiding in a cave. His devotion to God has not prevented their desire to kill him- in fact it is God's choice of him as the future king that has landed him in this trouble! Had God not shown such an interest in this shepherd boy, no one else would have bothered, either.