"Mr. Jones, your cholesterol has gone back up. Are you taking your simvastatin everyday?"
"No... Was I suppose to?"
This is usually followed by an awkward silence.
"Well, my last cholesterol was good and so I thought that I could just stop the medication."
For medications that need to be taken chronically, I have made it a habit to say something like, "You will likely need to take this medication for the rest of your life. If you make some dramatic changes to your lifestyle or you lose a lot of weight, we can talk about stopping the medicaiton. But don't stop the medication unless we talk about it or you are having a side effect."