Healthful eating and exercise can help to prevent many diseases including Type II Diabetes and heart disease. That does not mean that someone who eats well and exercises regularly can avoid going to the doctor on occasion. Prevention involves having routine check-ups that include cancer screening. There is also the likelihood that you will catch an infection that needs treatment or have some kind of injury.
One problem that many people face is that they have a slew of questions in mind when they schedule the doctor appointment, but forget them all when in the paper gown sitting on the examining table. The government has launched a campaign to inform people of the need to ask questions. They've even provided a list of the 10 questions you should ask. They also suggest writing down the questions you have, so you don't forget or get embarrassed when you're naked.