It is one thing to be deceived by someone else, but to be deceived by oneself is quite another. The Bible counsels us to be wary against self-deception and informs us of the conditions in which one is self-deceived.
While self-righteousness may be one of the main causes of self deception to an unbeliever, spectatorship is one of the main causes of self-deception to a believer. James 1:22 counsels all to be doers of the word and not merely hearers, for in just hearing and not doing, one deceives his/her own self.
We are asked not to be on the sidelines, spectating Christian life as a entertaining sport, but to be in the arena as a gladiator, fighting for the cause of the gospel of Jesus Christ and ready to die for Christ as a martyr (witness).
Let us not deceive ourselves.
Jesus likened the man that hears his words and not do it, as one who is foolish who built his house on the sand. Great will be the fall of that house, when the rain, floods and winds comes against it (Matthew 7:26-27).
Let us not be foolish and deceive ourselves.
James 1:22 (KJV)
22 But be ye doers of the word, and not hearers only, deceiving your own selves.
Matthew 7:26-27 (KJV)
26 And every one that heareth these sayings of mine, and doeth them not, shall be likened unto a foolish man, which built his house upon the sand:
27 And the rain descended, and the floods came, and the winds blew, and beat upon that house; and it fell: and great was the fall of it.
