I Pretend I'm Okay

Sometimes I pretend that its OK for me, but deep inside it hurts like hell. It hurts that its not okay. Its not fine. But what can I do? I need to say that I'm fine so that they won't know my true feelings. And it sucks to see them happy and youll pretend to be happy too. And it sucks. Knowing that they're hurting you without them knowing it. :(