I think what Nelly is trying to sing is that after all the bad experiences she has been through with people and previous lovers, she develops a rather cynical outlook on life. When it seems a new relationship is formed and she is in love again, she is reluctant to give all of herself emotionally. She is afraid to learn more about this person, about the "realness" of the relationship, and only to end up with more sadness and crying. She thought she had her life with her lover so beautiful and planned out, only to have to bitterly say goodbye when the relationship ends. Therefore, when the boyfriend wants more out of their relationship, all she can do is try so that she does not get hurt again.
I think what Nelly is trying to sing is that after all the bad experiences she has been through with people and previous lovers, she develops a rather cynical outlook on life. When it seems a new relationship is formed and she is in love again, she is reluctant to give all of herself emotionally. She is afraid to learn more about this person, about the "realness" of the relationship, and only to end up with more sadness and crying. She thought she had her life with her lover so beautiful and planned out, only to have to bitterly say goodbye when the relationship ends. Therefore, when the boyfriend wants more out of their relationship, all she can do is try so that she does not get hurt again.