From Dr. Caroline Leaf - Mind and Body
Dr. Caroline Leaf is a cognitive neuroscientist. Since the early 1980‘s she has studied and researched the Mind-Brain connection and did some of the initial research back in the late 80s showing the neuroplasticity of the brain. When Dr. Leaf uses the words 'undisciplined mind', she's not saying one should feel bad or guilty for having angry or fearful thoughts. They are totally normal. An 'undisciplined mind', means to allow negative (ex. angry, fearful, guilty, envious) thoughts to have 'free reign', or, to continue on without gently confronting them with Truth, or, God's word. Dr. Leaf's words below, echo/affirm this:
"We cannot afford not to, ”bring all thoughts into captivity to Christ Jesus (2nd Corinthians 10:5)"
To read the full blog article: https://drleaf.com/blog/you-are-what-you-think-75-98-of-mental-and-physical-illnesses-come-from-our-thought-life/