His main point is: there is a compound effect, ALWAYS, to your choices, behaviors, and habits. Whether you like it or not. He proceeds to give excellent points and tips on how to wisely choose our behaviors and regulate our habits.
What's interesting to me is how science and experience confirms the principles God put forth in His Word so many years ago. "Capture every thought and make it obedient to Christ"/"I beat my body and run the race"/"Say only what is good and kind"/"Whatever is good and pure, think on those things"/"Choose you this day whom you will serve" etc.
One thing the book left out: "Struggling with all HIS incredible energy, which so mightily works in me." Col. 1:29. We have the power in us that raised Christ from the dead! That's a whole lot of help!