"I am the healthiest person I know" so others might disagree? Such self-centered perception of "being healthy" is one of the reasons people fool themselves while actually having a healthy lifestyle instead of being actually healthy. Any exercise also has an impact on health, it can be not just "healthy" but also unhealthy at the same time, at the expense of overall health. Also, cancer does not discriminate lifestyles. It's chance. There is always risk. "I am healthy"-people only fool themselves that it cannot happen to them.