Life as we know, is never smooth-sailing and without problems.
We tend to grumble about life and when the grumbling gets intense, we will take it out on people.
We will resort to complaining about people, whether spoken or written.
But the fact is that complaining about people will not solve any problems; in fact more problems will be created.
And the fact is that we complain because we can't do anything to change the people that we are grumbling about.
That seems to be what Jesus is saying about the people of His time - they grumble, they complain and they criticise, but nothing good is coming out of it.
But in the 1st reading, the Lord, the Holy One of Israel says this: I, the Lord, your God, teach you what is good for you, I lead you in the way you must go. If only you had been alert to my commandments, your happiness will have been like a river.
So we know the solution to our grumbling, our complaints and our criticisms against people or situations.
We must turn to the Lord our God and learn His ways and walk in His paths.
As the Responsorial Psalm teaches us, may we also respond with this: Anyone who follows you, Lord, will have the light of life.