Yesterday I treated a patient with a severe toothache with a root canal treatment. Root canal problems can cause enormous pain. The good news is that I was able to quickly get him out of pain. The bad news is that if he had let me take care of the deep decay in that tooth 6 months before, when I saw the problem, he would not have suffered with pain or needed a root canal treatment.
I'm not a "told you so" person, so I didn't discuss any of that with him. I absolutely will never even come close to criticizing a patient. I'm here to help people; not make them feel bad.