Being a man, this isn't an easy one to answer but men do this also. I've done that a couple of times and it was a major mistake. For me, I guess I was just attracted to this woman and it was great at first and then nothing but jealousy over every female I talked to. We all make these mistakes in life and you don't always know that you are really making a mistake until the trust issues start. I can't really say why it happens but you sure learn from your mistakes. I know I have. I've learned to really get to know the lady before I commit anything anymore. Seems safer that way. I guess women do that for the same reason thinking the grass is greener on the other side. Really get to know them before you decide to change!