The habit of lying is a hard thing to stop once we have started. Why did we start? There are all kinds of reasons why people start. Sometimes it is a self-preservation thing. It started young when our mom's would ask us questions like "Who left the milk out?" Then there are the embellishment lies with our friends; the proverbial "fish story". These lies make us look good. There are the vengeance lies, to get an enemy in trouble. There are lots of different lies and lots of different reasons why we lie and once started it is hard to stop.
However, lying does not belong to the children of God. Our God hates falsehood and part of our transformation is to destroy the need for lies. It was part of our old nature, but now we are a new creation, with new and better habits; ones that glorify Jesus:
Do not lie to each other, since you have taken off your old self with its practices and have put on the new self, which is being renewed in knowledge in the image of its Creator. (Colossians 3:9-10)
The reasons for lying have been taken away. No longer is self the center of our being. We have no reason for self-preservation. We do not need to make ourselves look good. We have no hatred or ill-will toward our enemy. Jesus has become our everything and our only desire is to bring him glory and to allow his character to shine through us. Everything has changed. What once was is no more. A creation never seen before stands in its place; a blending of God and us; transformed by the power of God. Our hearts and minds have been changed forever, and our bodies will soon follow.
Yet, you might still be stuck in that habit. The reason for it is gone but the habit remains. It is similar to smoking. There is usually a reason why people start. Could have been a rebellious act, a thing to still nerves, a response to depression or stress. The reasons are gone but the habit is fixed and hard to break. How do you break the habit of lying? By telling the truth.
Every time you catch yourself in a lie, stop and tell the truth. Apologize and reverse course. Yes, it is embarrassing but after a few embarrassing incidents you will start avoiding the lie and the Spirit of God will lend you strength. "I'm sorry, I have no idea why I said that. The truth of the matter is ...." "I'm sorry, that was a le. The truth is ..."
Take off the old self with it's practices and put on the new self.
The new creation that we are is made in the image of our Creator. The transformation happened and is continuing to happen. The cross changed us and gave us the capacity to carry God's image so the transformation is ongoing. As we gain more knowledge of him we become more like him. We are being renewed in this knowledge. Now you have the knowledge that lying does not belong to our new nature; go and sin no more.