She keeps her heart guarded because she has been hurt before. Once upon a time, she trusted someone who ended up smashing her hopes into pieces, and she is worried about making the same set of mistakes again. She is worried about walking into the same kind of situation that broke her heart before.
She keeps her heart guarded because she has trust issues she is struggling to overcome. It is hard for her to believe that someone is being authentic with her when she has learned to expect lies. It is difficult for her to believe that anyone is serious about wanting to stick in her life.
She keeps her heart guarded because she has grown comfortable being alone. She is used to waking up beneath the bed covers alone and cooking for one. She is used to being the single girl, the unattached friend. She is okay with the life she is living, so she isn’t sure if she should bother to put herself out there.
She keeps her heart guarded because she feels broken inside. Her past romances have screwed her up, they have given her baggage too heavy to carry. If she’s being honest with herself, she isn’t really sure if she is ready for love. She is not sure if she can handle all that it entails.
She keeps her heart guarded because she knows that if she lets someone inside, then they will have the power to hurt her. They will have the ability to walk away with a piece of her. They will have the means to shake her confidence, to destroy her happiness.
She keeps her heart guarded because she isn’t sure if she believes in monogamy anymore. She has her doubts about everlasting love. She is skeptical about the idea of committing to someone forever, because all of the relationships she has seen in the past have fallen apart at the seams.
She keeps her heart guarded because she doesn’t want to get accustomed to having someone new in her life. She doesn’t want to forget what it’s like to live without them, only for them to walk away without glancing back. The last thing she wants is to get abandoned by someone that means the world to her.
She keeps her heart guarded because she has a poor self-image. She can’t imagine anyone ever falling for her. She can’t imagine a life of true love when heartbreak has been her reality. She assumes that anyone that enters her life is eventually going to get bored and leave her behind.
She keeps her heart guarded because she thinks that she is better off that way. It is her way of protecting herself. It is her way of avoiding the emotional pain that relationships bring.
She keeps herself guarded because she doesn’t want to love again, she doesn’t want to feel again, she doesn’t want to get hurt again. She is terrified of handing her heart over to the wrong person and paying the price for it. 
