When you still were living in darkness, there were many lies you allowed into your spirit to the point that they became natural to you. Darkness became natural to you and you had become children of darkness. You identity was rooted in things of darkness such as lying, sexual immorality, addictions etc.
But now that you are saved and are brought into the light. You now know through the Holy Spirit what is good and evil. You know the patterns of darkness and you avoid them. Yet still the lies from the past come to act as temptions to you to fall into sin. For example being tempted to lie even if its just a little or to drink just a little if you used to be an addict.
You will be tempted with the things that had kept you in darkness for so long, the things things that made you fall in the first place. Now is when you must stand guard to be able to recognize those lies from the devil. Because the lies wont stop, instead they will keep on coming to you till the day you give in and return to darkness because thats where the devil wants you to be. You must avoid giving in to sin because its the very thing that separated you from God.
Instead resist the devil and He will free from you James 4:7. At the end of the day you must ask yourself if this lies are worth losing the relationship you have with God. Theres a reason why you were removed from that life, dont look back and fall for the same things that doomed you to death in the first place.