Why didn't i see?

Why do you hurt me so bad
when knowing what your doing
i am nothing without you
my life you keep ruining

you know exactly what to say
to make all forgotten
then you switch and turn around
your heart becoming rotten

why do i always stand by you
no matter what you've done
tear me apart left hurt and sad
my friends told me to run

but still causing hurt with every word
you carry on again
so spitefully shallow you can be
bringing unbearable pain

for you i left my dearest friends
you were all i needed
thinking this time it may last
by now you had succeeded

you could make me feel so special
knew how to make me smile
and as i fell into your trap
the pain seemed worth my while

but yet again those spiteful words
were used to brake my heart
left torn, broken and forgotten
wonder if this feeling with ever part

my first poem, please comment on how i can improve