There are difficult situation that comes in our lives that God allowed and in the same situation He create grace, because we spend time complaining we miss the grace that was provided at that time. Exodus 15:23-25 Now when they came to Marah, they could not drink the waters of Marah, for they were bitter. Therefore the name of it was called Marah. And the people complained against Moses, saying, “What shall we drink?” So he cried out to the LORD, and the LORD showed him a tree. When he cast it into the waters, the waters were made sweet. There He made a statute and an ordinance for them, and there He tested them.
You can be involved in a serious car accident, where people thing no one can survive but you come out with minor injuries. When concentrate on the car that you lost, you miss the greatness that should be celebrated, your experience with God during the accident.
You can be given an unexpected debt that you must pay and at the same time money you did not expect comes your way to cater for the problem that devil thought will give you a headache and you miss the grace.
God had favor upon the people of Israel but all they did was complain. Complaining made them miss appreciating the miracles that God performed before their eyes. Complaining not only make us miss God, God does not like it. Numbers 11:1 Now when the people complained, it displeased the LORD; for the LORD heard it, and His anger was aroused. So the fire of the LORD burned among them, and consumed some in the outskirts of the camp.