Baptism into Christ is necessary for salvation. There is no doubt to this reality. However, faith in Christ doesn't stop someone from leaving Christ for a worldly lifestyle or worldy passions.
A lifestyle in Christ is just like it sounds - a lifestyle. It takes determination, passion, and a lifelong committment. Fortunately, God knows that all Christians still suffer from sinning (cf. 1 John 2:1-6). Yet, others will wander completely from the truth. Scripture doesn't teach that these people have to be baptized into Christ again but it does teach that they need to repent of the incorrect lifestyle that they are living and become truly committed to the teachings of Christ again. [Note, Simon the Sorcerer Acts 8:9-25]. Simon was expected to repent and pray. James teaches that someone needs to come back from their wanderings.
Are you baptized into Christ and committed to Him. If not humble yourself before God and come back from your wanderings.
The Lord's humbled . . . John A. Reeves