More on Numbers 11:1a

The reason it says they became like those who complain of adversity is that their circumstances were not adverse! Though the complaint against the manna starting in verse 2 is not what verse 1 refers to, we can see they had nothing to complain about with just cause. They had miraculous food and water and their clothes did not wear out. Their circumstances were not adverse, abut they complained. Thus the anger of the Lord was kindled.

Lately, I have found myself complaining as though I am in adversity. Really, it's been all my fault that I have bad days and felt unfulfilled. I have not been in close fellowship with the Lord and that throws off my entire day. Seeking fulfillment in other things that are normally fun does not result in true fulfillment. Thus I have complained to the Lord as though in adversity. But really I am more like the prodigal son, trying to find pleasure apart from the Father. That doesn't work! I gladly return home where He provides all the pleasures and fulfillment I need (Luke 15, Psalm 16:11).

In contrast to the Israelites complaining like those in adversity, David complained when in adversity, where it was appropriate: Psalm 55:2-3,16-17

Give heed to me, and answer me;
I am restless in my complaint and am surely distracted,
Because of the voice of the enemy,
Because of the pressure of the wicked;
For they bring down trouble upon me,
And in anger they bear a grudge against me.

As for me, I shall call upon God,
And the Lord will save me.
Evening and morning and at noon, I will complain and murmer,
And He will hear my voice.

When truly burdened by something, we ought to "complain" about it to the Lord: Psalm 55:22, 2 Peter 5:7

Cast your burden upon the Lord, and He will sustain you;
He will never allow the righteous to be shaken.

Casting all your anxiety upon Him, because He cares for you.