As you correctly implied, sometimes, we fail to see ourselves and evaluate our performance or behavior, which is quite normal by the way. With regard to this part of human nature, we should compensate for this lack of self-evaluation or self-assessment by asking for feedback openly.
To evaluate performance more accurately, we rely heavily on the circle of our friends who know us sufficiently and are benevolent and sincere to us. We can also reciprocate this productive favor and give them our feedback in return. I most treasure the friends who give me their valuable feedback especially in private, and I consistently provide my friends with feedback only when we are alone.