Have you had the experience yet of getting frustrated with your son and speaking to him only to realize that you sound just like your mom or dad? Or have you made a mistake and the voice in your mind that tells you that you've screwed up is one of your parent's voice?
I have. I still do. Regularly.
The more time I spend parenting my kids, the more I realize that my default is to do and say the things that my dad did with me. I don't even really have to think about it or try, it just happens. In my case, that's not a bad thing. I think my dad did a pretty good and level-headed job teaching and guiding me so I don't feel like passing that on to my kids is wrong.
What does strike me with fear, however, is the realization that my sons will do the same thing with themselves and their kids. That raises the stakes tremendously.
The way that I speak to my kids is going to shape the voice in their head that becomes their conscience.
So what? If it's worked thus far, why worry about it?
Working from the assumption that every parent is working to make their kid more successful than they were, this knowledge enables you ensure that you're speaking to your son in a way that will encourage behavior that will help him succeed in life.
If your voice in your son's head tells him that he's a lazy screw-up that can't do anything right, do you think he's going to get up off his lazy ass and get stuff done? No, he'll meet those expectations and stay on the couch playing video games.
If your voice in your son's head tells him that he's capable of so much more and that he'll figure it out if he just keeps trying in spite of falling short of his goals, he's more likely to keep going and trying.
Think about what you're saying to your son about himself. Think about the words that come after you say to him, "You are ..."
Do those words reflect the sort of person you want your son to become or are you guiding your son down a path that is the opposite of what you want for him?
I should mention that you shouldn't lie. Kids are great at spotting bullshit. If your son is stealing things, don't tell him, "You are such an honest young man." Instead, paint a vision for him of what he's capable of becoming. Tell him, "You can be an honest young man." Be honest with him about where you see his behavior now and point him towards the sort of behavior you want to see in him.