I think you're the reason why:
Why I have insomnia,
Why I lay awake through the night, restless and disappointed
Why I fall asleep to lies and impossibilities
Why I wake up in the morning and swear at my reflection

I also believe that you're the reason why:
Why I have a heart
Why I breathe air and blink
Why I trip over that air in the hallways
Why I smile, trying to reassure myself that we never would end up together