I know I shouldn't...

I know I shouldn't think of you,
When the world really gets me down,
I know I shouldn't expect you to be there,
To help get rid of my frown.
I know I shouldn't hate you,
But inside I really feel,
I know I shouldn't dwell upon our past,
But the love we had felt so real.
I know I shouldn't want to hold you,
You're with her and you're happy now,
I know I shouldn't still love you,
But dismissal my heart won't allow.