Always a part. Never a whole. If only half grows I shrink. What am I?

Answer: A fraction

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Always old, sometimes new. Never sad, sometimes blue. Never empty, sometimes full. Never pushes, always pulls. What am I?
Always well dressed, but I never fly. Black and white, sometimes in a tie. I swim and slide, and dance and glide, With one person by my side. What am I?
An action done on mosquito bites. What am I?
Angels and pilots work with me. What am I?
Anywhere I am, there is none. If you dare ask 'what am I'? I'll be gone... What am I?
As a state in America. I am round on both sides and high in the middle. What am I?
As a stone inside a tree, I'll help your words outlive thee. But if you push me as I stand, the more I move the less I am. What am I?
As beautiful as the setting sun, As delicate as the morning dew; An angel’s dusting from the stars, That can turn the Earth into a frosted moon. What am I?
As your ideas grow, I shrink. What am I?
At a bank without money I’d go on a spree. The more I like you, the more you hate me. What am I?
At the sound of me, you may stomp your feet, but you may also dream or weep. What am I?
Before I came, the world was darker, that's true. But beware, I can also kill you. What am I?