It’s usually folly to believe you’re better than you actually are. But there may be times when it’s not. It depends on the subject or activity, and it depends on what’s at stake.
If the cost of being ignorant is high, then it’s better to be totally honest with yourself. If the cost is low or non-existent, then the bliss of ignorance may be worth it.
For instance: In sports, thinking you’re a champion before you’re a champion may actually help you become one. But thinking you’re a world-class poker player when you’re not could lead to ruin.