"Let no man deceive himself. If any man among you seemeth to be wise in this world, let him become a fool, that he may be wise. For the wisdom of this world is foolishness with God. For it is written, He taketh the wise in their own craftiness." (1 Corinthians 3:18-19)
We can deceive ourselves. What we feel about ourselves can be completely contrary to what God thinks about us and that's where we need to be tuned to the Holy scriptures as a mirror and introspect ourselves. The Corinth church in all probability had the rich ones and also the slaves. People thought that more a person was wise, the more they had riches. People in fact thought that they were wise in their own ways and they followed their leaders. St. Paul in this epistle reiterates the importance of having a proper understanding and realisation of the life in Christ.
The moment we feel wise in the world, we should understand that it's foolishness in the sight of God. The more we are self-obsessed we block the work of God in our life. Pride has this subtle way of entering into people's lives. It's therefore very important that we keep directing our thoughts to the word of God and properly understand where we stand in the eyes of God. We need to become impoverished, blind, foolish to appropriate the things of God. Spiritual understanding and revelation comes to those who are humble and contrite in spirit. Let's have an attitude of gratitude and humility and may we receive it all from His precious hands. Let's not live a life deceiving ourselves.
For further reading: James 4:6, Revelation 3:17-20