When we operate in contrary to our nature (identity in Christ) it is quite natural that we feel miserable. The flesh wants to do it but we feel miserable after doing it. Knowing the fact that I am going to feel miserable after this, why do we still do it?
I like an analogy Bob George uses. It goes something like this: A person who lives on the street and eats from the dumpster everyday was offered a lifetime free ticket to a cafeteria full of food. He was so happy and asked, Are you sure that I can eat anything I want from this cafeteria? Sure you can! Are you sure it's free? Yes, it is absolutely free! But he then asked, Can I eat from the trash bin as well?
As believers in Christ, God has provided (freely) everything we ever need for life and godliness, but still we want to eat some trash once in a while. I think that is ridiculous. Why would we do that?
I know that after yelling at my wife I am going to feel miserable, so why do it?
I know that after over eating I am going to feel miserable, so why do it?
I know that after looking at the porn I am going to feel miserable, so why do it?
I know that after steeling I am going to feel miserable, so why do it?
(...fill in anything which is contrary to the Spirit who lives in us)
We don't have to do it! Thats for the world, not for us. Our needs are met in Christ. We have everything we ever need.
I am not talking about being obsessed with sinless perfection or being preoccupied with behavior modification or anything like that. We have a great pasture in Christ, then why would we want to go to the dirt? and then feel miserable?
I think the reason we do that is because of the lack of knowledge of the treasure we have in Christ. That is where the 'renewing of the mind' comes in to picture. Our mind needs to be constantly renewed and reminded of who we are and what we have in Christ.