We might be relieved if God placed our sanctification only in the hands of trained professionals, but that is not his plan. Instead, through the ministry of every part of the body, the whole church will mature in Christ. Paul David Tripp helps us discover where change is needed in our own lives and the lives of others. Following the example of Jesus, Tripp reveals how to get to know people and how to lovingly speak truth to them. - Back cover.
Key Quote = "We must not offer people a system of redemption, a set of insights and principles. We offer people a Redeemer.”
The author rightly explains that the root of all problem behaviour is sin in the heart. However, he doesn't allow for medical/neurological problems which may contribute to wrongful thinking and behaviour. These can be deeply ingrained and the approach of the author in places is too simplistic/overlooks reality.
For a Christian, balance is needed to ensure we do not place too much emphasis on secular psychology and its solutions, but also where there are medical issues these need to be recognised and treated properly and not just explained away as sin in the heart.
The bottom line is that God can change anyone and deal with any of these issues but how God chooses to work in the life of a person may be different in each case.