Doubt is planted in a very subtle way and so is the confidence.
Our subconscious mind process words from different people differently. What this mean is that we are likely to give more importance the feedback given by our closed people than the distant or unknown ones.
An encouraging word from your father can give you an adrenaline rush or can depress you like hell. We all have people around us whom we influence in our daily lives, we all have the power to empower our closed ones and we should do it more often.