At the commencement of Matthew 5 we find the Lord Jesus pronouncing blessed a certain class of people. They are not named as "believers" or saints," but instead are described by their characters; and it is only by comparing ourselves and others with the description that the Lord Jesus there gave, that we are enabled to identify such. First, He said, "Blessed are the poor in spirit." To be "poor in spirit" is to have a feeling sense that in me, that is, in my flesh, "there dwelleth no good thing" (Rom. 7:18). It is the realization that I am utterly destitute of anything and everything which could commend me favorably to God’s notice. It is to recognize that I am a spiritual bankrupt. It is the consciousness, even now (not years ago, when I was first awakened), that I am without strength and wisdom, and that I am a helpless creature, completely dependent upon the grace and mercy of God. To be "poor in spirit" is the opposite of Laodiceanism, which consists of self-complacency and self-sufficiency, imagining I am "rich, and in need of nothing.

~ A.W. Pink The Nature and Basis of Assurance