weakest when strogest

I'm the weakest when I'm the strongest.
I hide my sorrow behind my anger.
When I wanna cry I say things I don't mean.
I sing when I seem to lose everything.
I smile when I wanna frown,
but I stay strong so I won't let you down.
That way I can watch you be happy and keep you remembering me,
even if it's hard on me to see you so happy.
I will keep to myself and never shed a tear.
I will stay strong until being strong defeats me.
That way I hope you will always remember me.