love and relationship

"If you love someone, let it be and set him free, if he comes back to you, it's meant to be."

One of my good friends once described me: "You always know how to grab opportunities to get what you want, besides love," which is really true.
I'm just extremely pessimistic and insecure about love and relationship.
Ten years ago I still believed that true love can change everything, but now I've lost this kind of courage.
It's always like this; when I finally met the guy I like, he just doesn't love me back as much as I love him.
Therefore I always fail to maintain a long-term relationship and most of the times a loser.
The thought of "It must be because of the fact that I'm not good enough" always comes to my mind.
Although I so much want to be a wife and mother in the future, somehow I just have a feeling that I won't be able to make it.
I can't help but sometimes being afraid of being too close with the guy I like because I don't want to get hurt.This traineeship will be just perfect if I can also overcome this big problem of mine.