I will not make the same mistakes that you did
I will not let myself cause my heart so much misery
I will not break the way you did
You fell so hard
I learned the hard way, to never let it get that far

When Lily's mother had left her father her life had changed. Before she had been happy and carefree but her mother's affair had changed her father and he had changed her.

Because of you
I never stray too far from the sidewalk
Because of you
I learned to play on the safe side
So I don't get hurt
Because of you
I find it hard to trust
Not only me, but everyone around me
Because of you
I am afraid

Every time he had hit her she had promised herself that she would never fall in love. She still loved her father but she knew the man who raised her wasn't him. He was someone else.

Her father was kind, forgiving and this man was rough, harsh and without mercy. She had learnt to be so careful to never anger him. She got top marks, she tried hard and she did everything he asked. He had stopped hitting her eventually but then she got The Letter. The Letter was the one that had told her she was a witch and it had plunged her life into darkness once more.

I lose my way
And it's not too long before you point it out
I cannot cry
Because I know that's weakness in your eyes
I'm forced to fake a smile, a laugh
Every day of my life
My heart can't possibly break
When it wasn't even whole to start with

In a moment of kindness he had allowed her to go to Hogwarts. But she had paid her price. The beatings that had finally stopped began again and every time she was home she endured vicious beatings. She wouldn't cry; when she had cried he had just hit her harder. So she had learned not to feel, to hide her battered heart under a kind smile and a mask of niceness.

Because of you
I never stray too far from the sidewalk
Because of you
I learned to play on the safe side
So I don't get hurt
Because of you
I find it hard to trust
Not only me, but everyone around me
Because of you
I am afraid

When she had reached Hogwarts she studied as hard as she always had, hoping to please her father. She didn't please him; she angered him. She had now learnt how to defend herself against him but never did. Instead she let him beat her and used healing and concealment charms. She had no close friends. She did not want anyone to know her secrets and she didn't trust herself or anyone else. But there was one boy who despite all her rebuttals had kept coming back, trying to earn her trust.

I watched you die
I heard you cry
Every night in your sleep
I was so young
You should have known better than to lean on me
You never thought of anyone else
You just saw your pain
And now I cry
In the middle of the night
Over the same damn thing

She remembered the time when she had heard him crying at night and wanted nothing more than to help him. But what could she do, she had only been 8 at the time. He had wanted her to support him but she had never known how to. Now she cried at night because of what he had done to her and because she could never trust that boy with messy black hair and gentle hazel eyes.

Because of you
I never stray too far from the sidewalk
Because of you
I learned to play on the safe side so I don't get hurt
Because of you
I tried my hardest just to forget everything
Because of you
I don't know how to let anyone else in
Because of you
I'm ashamed of my life because it's empty
Because of you
I am afraid
Because of you

Now she was afraid to trust him. She was alone and afraid because of him.