I am currently reading the book "The Mortification of Sin" by 17th century Puritan John Owen. The book concerns the subject of killing personal sin in our lives. The first half of the book is very powerful thus far, but Owen mentioned something in chapter 5 that really struck me as something for us Christians to be constantly wary of; and that is to not be so overtly focused on ridding particular sins from our lives that we unknowingly let down our guard and allow brand news sins to slip in without realizing it, and thus still be slaves to sin. Owen's stated it this way, "He that changes pride for worldliness, sensuality for pharisiasm, vanity in himself to the contempt of others; let him not think that he hath mortified the sin that he seems to have left. He hath changed his master, but is a servant still."
There is perhaps no other time in our lives when we are more open and susceptible to absorbing new sins in our lives than when we let down our guards after accomplishing the mortification of old sins. The words of Jesus can and should be applied here, when He said, "Watch and pray that you may not enter into temptation" - Mark 14:38. Jesus is not suggesting that we keep an eye on the sins we are currently committing, but that we prepare in advance to be on guard and pray against new sins that we will be tempted with in a future sense. This command of caution by our Lord was so important that it was recorded and repeated by Matthew in his Gospel as well (Matthew 26:41).
Mortifying particular sins in our lives should never give grounds for celebration and cause defensive leniency resulting in the temporary lowering of our spiritual walls of protection. May we always be in pursuit of mortifying our old sins, while simultaneously being fully conscious of the real possibility of being tempted and attacked by new sins at precisely the same time of our victories.
"Watch and pray that you may not enter into temptation." - Mark 14:38