Ways in which true beliefs can be bad for you

• Knowing how to build a nuclear reactor, which then explodes. "A little knowledge is a dangerous thing."
• Disbelief in god when non-believers are killed. Disbelief in the socially dominant ideology when this is punished by society. Even if no one believes it, revealing non-belief can be fatal.
• If you accurately know your own abilities, you may not take risks which would be good for you. You may be less confident which could be bad for you.
• Self-deception and the having of emotions can be good for you. Instead of faking an emotion, you have it for real, and use this to get what you want.
• Anti-natalism. If you don't believe life has a purpose, you are less likely to procreate.