Psalm 142:1-2 I cried unto the Lord with my voice; with my voice unto the Lord did make my supplication. I poured out my complaint before him; I shewed before him my trouble.
When in trouble, we respond by crying unto the Lord. We cry out loud with a voice, and we cry tears of sorrow. In making a prayer I pour out my complaint and tell Him my trouble. It is not that God needs to know my problems, for He already knows, but I need to say it aloud and tell Him so that I know where answers come from and deepen our relationship.
This kind of complaining is putting into words what we are experiencing with the faith that God hears and cares. A sinful kind of complaining is blaming God for our problems instead of ourselves, like Israel in the wilderness. A complaint can be either faith that God is involved with our lives or unbelief that He is really good. Either way God hears our cry and answers with manna. So it is good for us to “pour out our complaint” with faith that God hears and cares. It is not good for us to just gripe about our misfortunes and blame God for our troubles. But we repent, believe, and pray.