ANSWER: Lack of self-knowledge and self-confidence can make one vulnerable to fallacious reasoning, because the person will want to use fallacy to explain a point which he/she does not have a proper knowledge in.
Example: someone asked you to buy a cream from Obi. You don't want to buy that cream from Obi but from Ada, and you don't have any proper knowledge about the cream, you just respond by saying, why not I, buy the cream from Ada which has a smooth skin, instead of Obi, which has a rough skin, if Obi's cream is good, he could have used it to heal his rough skin. You replied like this because you don't have a self-knowledge about the constituents of the creams sold by Obi and Ada, and you neither dont know how to determine the best cream for his body.
To give a critical thought to the above example, your statement is fallacious, but you can overcome those fallacy in your statement if you have advised that the two creams sold by Obi and Ada should be checked to know the one that is best for his skin, considering the fact that Obi applies his cream but it doesn't change his skin roughness, while Ada skin is smooth and shinning as she applies her cream.