Then why should you absolutely have to insist on his own? Much easier wise girl to agree with the man, but still praise his mind and intellect. Even if you know that he is wrong. Then he receives confirmation error of his views and understands that his girlfriend is much smarter than he thought. But you do not quarrel, and the young man begins to respect your words and take them into account.
Remember how all your quarrels begin, what the theme for you is the most dangerous. Come together with her boyfriend to a peace agreement on the disputed issue, think it really important to keep talking about it. If the topic is really important and urgent, find a compromise that will satisfy both of you.
Learn how to control his emotions. Spur of the moment we can say and do what is sure to be sorry later. There is a very simple way to deal with nerves - count slowly to 5-10 (the value of the number depends on your temperament), before voice their thoughts. Gradually, this method becomes a habit when you see its positive results.
Your relationship will move to a new, much higher level, without quarrels and scandals. Disappear fear of talking and communicating with her boyfriend at all. You will realize how nice can be goodbye, if you know what you cope with any situation and do not give her to get out of your control.