When Yaakov Avinu ran off with his family and possessions without telling Lavan, Lavan gathers a few of his men and proceeds to chase after Yaakov. When he catches up with Yaakov, an interesting conversation ensues. Lavan accuses Yaakov of stealing his idols, Yaakov denies the accusation and allows Lavan to search all his possessions. When the search bears no fruits, Yaakov vehemently protests Lavan's unscrupulous behavior:
"You have searched all my possessions, what have you found from the possessions of your house; place them between my brothers and your brothers, and they will decide between the two of us. I have been with you for twenty years - your sheep and goats did not miscarry, and I did not eat any rams of your flock. I did not bring you killed animals, rather I took the loss; from my hand you claimed it whether it was stolen by day or by night. During the day the heat devoured me as did the ice by night, and sleep was held back from my eyes. I have spent the past twenty years in your house: fourteen years I worked for your two daughters and six years for your sheep and you changed my wages one hundred times!" To which Lavan responds, "The daughters are my daughters, the sons are my sons, the sheep are my sheep and everything that you see is mine."
Rav Wolbe comments (Shiurei Chumash) that one cannot help but be amazed at Lavan's response. Yaakov just gave a lengthy explanation of how everything was rightfully his down to the very last penny, and Lavan makes no mention of anything Yaakov said. He simply states that everything in sight belongs to him and not to Yaakov! The Mashgiach explains the rationale behind this behavior. There are times when there is a conflict between what logic dictates and what one desires (i.e. his negative middos). In such a situation, it is useless to try to argue logically with such a person. Explanations aimed at the seichel will not succeed in changing preconceived notions that are a product of one's faulty middos. Lavan simply "didn't hear" what Yaakov said, because he didn't want to hear. His lust for money wouldn't allow him to understand that all the possessions were rightfully Yaakov's.
This is the danger of bad middos. When one is entrenched in a mindset that is borne out of his negative desires, even a completely logical argument might not succeed in causing him to change that mindset. However, if we are interested in improving our middos, we will be granted siyata dishmaya, and we will surely succeed in rectifying them.