Patients don't always do what you want or expect them to do. My professors have often said that it's easy to know what needs to be done to fight a disease, but it's hard to make sure the patients actually do it.
Here's an example to illustrate the point. This is true story. No joke.
A women brought her teenage son in my professor's office one day because he had a red eye. He looked at it and saw that it was a bacterial infection and wrote him a prescription for some antibiotics. He gave them the paper with the prescription and told the mom to make sure her son took it every day, and then to come in again for a follow-up exam in a week.
A week later, the mom brought her son in again and the infection had gotten worse. He couldn't understand what was wrong, so he asked her if he's been taking the prescription.
"Yes, every day!" she replied.
"Okay, show me how he does it."
The women pulled out the piece of paper with the prescription on it and she proceeded to rip a small piece of it off, rolled it into a ball, and popped it into the boy's mouth. She had been giving her son pieces of the paper instead of filling the prescription.
Moral of the story: don't assume anything. If you are going to expect the patient to do something, make them show you that they know how to do it before you let them out of the office.