In the the life of a woman, usually at some point, she feels as though she is not good enough for anything. At some point she feels as though she will be alone for her entire life; in the romantic sense. Although she dates, she cannot find a partner who is right for her and who meets her standards. When she does find a partner who is right, it rarely works out because the person she's fallen for never wanted something serious to begin with, causing a broke heart.
In the life of a man, at some point, the only thing wanted is sexual interaction. He feels as though he's better than enough for many of the people he meets so he only shares a snippet of who he really is. He does was a romantic relationship, but is not entirely sure when he wants one and does nothing to find a girl to settle down with because he has too much fun messing around. Little does he know, he is breaking hearts of many.
With that said, these roles can often be switched.