Why Do We Struggle With Legalism? (or Lawlessness)?

  I have been learning a lot about guilt and shame in our counseling classes and I see a lot of similar patterns among people. Many people suffer with guilt. Some of the reasons are valid, like they have done something wrong and they want to make it right, but don't know how. Others think they have done something so evil that God can't possibly forgive them.
  I was in a meeting this morning and the lady, Ruthie Delk, was teaching on this very subject. She was helping us to understand that when we have a small view of God, and small view of sin, our view of the Cross will also be small. She used her hands to illustrate this point. She was showing distance by holding one hand above the other and the hands illustrated her shallow view of God. The space between her hands showed the resulting view of the Cross.
   When we rightly understand who God is, and the gravity of our sin, we have a clearer picture of the Cross, and its magnitude. So why do so many people struggle with perfection and legalism? It is because we want to bring something to the table. We trust God for some things, the things we can't do, but we forget God, or try to do many things in our own strength, striving for some kind of approval, from God and also from others. Instead of resting in the finished work of Christ on the Cross, we feel like we have to add something to that. Like C.J. Mahaney would say, "The only thing I bring to the Cross is my sin." The answer to this problem is to understand the Gospel correctly. We have to understand that sin is not necessarily what we do (although there are things we do that are sin), but  sin is at the core of our being. For example, if we made a decision to never tell a lie, we still would be sinners at heart because sin is at the heart of every person. It is our fabric. The lie is a symptom of our sin nature. It's kind of like being sick. You can find all kinds of over the counter medications to help relieve the symptoms, but taking care of the symptoms does not solve the problem. You are still sick. Another way to look at it is, if you took a fruit tree, and removed all the fruit, you would still have that type of fruit tree. It would be bare, but it would still be a fruit tree of that sort.
"I think the problem we have in understand the Gospel correctly, is that we think sin is a behavior vs. a heart condition. We label things that we do that are wrong, as sin. Yes, they are sin, but sin starts in our hearts. These actions could be better described as a symptom of sin. We could cut off all the symptoms of sin, but we, at the core of ourselves, will still be sinful."