Matthew 5:6 “How blessed are those who hunger and thirst for righteousness! for they will be filled.”
Obviously it does not mean that we feel and we can attain unto this righteousness by our own efforts and endeavor.
That is the worldly view of righteousness which concentrates on man himself and leads to the individual pride of the Pharisee. Or to the pride of one nation as against other nations, regarding itself as being better and superior.
Recall, being poor in spirit is a negation of every form of self-reliance so this is not something you can do on your own.
It means a consciousness of our need, of our deep need.
I go further, it means a consciousness of our desperate need.
It is not a passing desire.
Hunger is something deep and profound that goes on until it is satisfied.
It hurts, it is painful.
Just like actual, physical hunger and thirst.
It is something that goes on increasing and makes one feel desperate.
It is something that causes suffering and agony.
To be hungry is not enough; I must really be starving to know what is in His heart towards me.
When the prodigal son was starving he turned to his father.
Now that is the whole position.
This is a dead serious summary of chapter 7 in Studies in the Sermon on the Mount by D. Martyn Lloyd-Jones.