Is "doing according to one's best understanding" a protection from wrong-doing?

A common belief is that, if one conducts himself "as best he can" (in the best ways he understands and knows), then would be a protection from -- or an excuse for -- wrong-doing. For example, "I answer with best effort and understanding..." Under the context of truth, the Dhamma, is this just a naive thought of foolish people? Or can such be rightly justified as something an Awakened would approve? *[Not at all given for trade or keep people caught in corruption]*