What is anxiety?

Anxiety is waking up in the middle of the night
Heart pounding
And senses spiking

Anxiety is walking out onto a cold balcony and staring down at a street full of taxi cabs,
And thinking,
"Should I jump...?"

Anxiety is full body shaking
And mind convulsing
While you're sitting completely still

Anxiety is standing in a full room
And feeling completely alone
And enclosed by an invisible box

Anxiety is the voice rising torture that fills your vocal cords and chokes you until you can't breath, and you're grasping at your lungs, trying to fill them with the air you can't seem to get
Anxiety is gasping, and gasping, and gasping