Let's say this relates to a diet. A possible paraphrase would then be:
1. Those who had resolved to comply with the diet were not only...
2. If your reaction to X is "mindful", you think about your reaction to X, and perhaps modify your behaviour accordingly. If it's "mindless", you don't: you simply react. In the context of "disease", "active" and "passive" might mean much the same.
3. Fear alone can make you fail. If you fail only because of fear, it's possible that the failure is unnecessary. Understanding the context of something may eliminate fear. You may then be in a position to succeed.
Does that help?