It is distinctly possible to be self deceived. And to be self deceived in the matters of faith, is of eternal significance.
2 Corinthians 13:5, says to “Test yourselves to see if you are in the faith; examine yourselves! Or do you not recognize this about yourselves, that Jesus Christ is in you—unless indeed you fail the test? “
In other words, Paul does not assume that everyone who professes faith in Jesus has living faith in Jesus.
James says it is entirely possible to listen to the Word and not hear the Word and therefore be self deceived. That is one who does not have a compassionate heart, a clean life or who lives a humble life, then they might want to reexamine themselves and test themselves again.
Just to consider oneself as within the framework of being a Christian is not sufficient. Since James loves those to whom he is writing, he warns them about what is a clear and present danger.
Speaking for myself, I have, personally experienced, on more than once instance, pastors and groups of people in churches (a.k.a., congregations) who exhibited little in the way of Fruit of the Spirit of God but who were very good at discrediting anyone and everyone who did not fit their mold.
They are very good at appearing good and doing good works on full public display and for public consumption, but, privately were troubled by envy, pride and even resentment.
Their public display of faith was carefully but primarily and ostensibly emotional. Frequent outbursts of emotions, such as speaking in tongues, proudly announcing their accomplishments, ranking themselves in order of achievements compared to others is their habit. If these things were, perhaps, intermittent behaviors, one could let them pass. But, when they are the staple, one has to wonder, “Is this the behavior of Christ, Himself?”
Here is a sermon by Alistair Begg address this issue. It was a great reminder to me for my conduct. Maybe it would be helpful to others? https://www.truthforlife.org/resources/sermon/false-faith/
The reason I bring this up is for the same reasons Pastor Begg presents in his sermon. Please, do not be deceived. These days are dangerous enough. Find your refuge in Christ, and Christ only – hide His Word in your heart and it will become your hiding place! Your Brother and Friend, Mike Young