A thought from Owen's Mortification of Sin in Believers on Romans 8:13:
Mortification from a self-strength, carried on by ways of self-invention, unto the end of a self-righteousness, is the soul and substance of all false religion in the world. --John Owen
In other words, fighting sin under your own power only creates more sin. What is the remedy?
The principal efficient cause of the performance of this duty is the Spirit.
Therefore, seeking to be filled with the Holy Spirit is to fight sin!