Honesty is an important part of theology. What I mean is theology needs to match reality.
You see many preachers and theologians concerned with holy living over simplify sin out of a great concern for loose living. They understand grace but are afraid and like to focus on works.
At times you will see them squirm in a small group setting when people are honest of their struggles in faith. You see they are concerned by the reality of life and wish for people to live well and often it is easy to reject the reality.
The reality of sin is that it is not ideal and holiness is something to strive for. But trying to hide the reality of the human condition and act as if the sinful thoughts of people are abnormal is not helpful.
You see we must start by first accepting the problem. That is why the admission of sin is necessary for faith. We can't accept grace if we don't believe we need it. .
The same thing is true with sanctification. We can't grow if we don't know what we need to grow from.
This is why many people who feel very holy tend to be the least holy. You see they have no idea of their sinful tendencies and thus have little idea of where they need to grow.
Often those aware of their sin are making progress on it. God can use the knowledge of their sin to help improve them. It is always difficult to fix what we do not believe is broken and that is why accepting the reality of human life is important.