The White Door - short story (POV is through a child's eyes)

The hospital gown is light. Bright lights glare at me, starched sheets covering the bed. 
My limbs are light, and my mind grey. I must be dreaming. Or dead. 
Big Sister told me that when you die, you become a star in the sky. This doesn't look like the sky. 
I shake my head. What ever it is, it's a numbing feeling, being here, but I'm glad for it. 
I don't remember leaving my bed, but I'm suddenly standing, a steadying hand on my IV drip. Cold tiles meet bare feet, and I slowly walk.
Walk away from the hospital room. Tiles blend into cold concrete, and then still nothingness. I'm in a room of black, and there's a white door, a stark contrast against the dark room. 
My mind is blank, but my heart still beats. Adrenaline thrums steadily in my veins. My steps are faster, and maybe a little sloppy - I nearly fall - but I don't care. I'm nearly at the door, just a few metres. Maybe I'm delirious, or hallucinating, but I can hear a song. A warm lullaby that pulls me towards the door. 
I've reached it. My excitemend suddenly falls. Twists into something like fear, and now I'm hesitating, my outreached hand faltering.
That's when I feel a cool hand meet my grasp on the IV drip. It closes around my fist, a gentle encouragement.
I inhale, and open the door.
A starry night meets my eyes. Lush greenery and open grass stretch out for miles, with dew embracing every inch of open surface. A small laugh escapes me, and then I've dropped onto my knees, eyes wide with disbelief.
I'm dizzy with happiness. My laughs mingle with the songs of larks, and the rushing sounds of a brook. 
I run and play for as long as my legs hold me up. My laughter echoes across the space, and I laugh even more at that. I find nightingales and catch floating dandelion heads. At times I nearly forget to pull along my IV drip, and get reminded by the sudden pain on the back of my hand as the needle nearly gets pulled out.
Eventually, I tire. My heart beats loudly, and my breaths are short and fast.  My legs ache, but I hardly notice the pain. I let myself down onto the prickly grass, and then giggle when it brushes my feet, tickling me. 
The gown is quite big, I quietly muse. My figure looks exaggeratingly small clothed in it. My hands are quite small too.
Smaller than Big Sister's.
'Huh?'
I look around. I don't remember Big Sister being with me. 
Where is my sister?
I'm panicking. I try to run, but the IV drip pulls me back. I try to pull it along with me, but it's suddenly too heavy. I can't breathe. Tears run down my cheeks.
I try to run, again, my grip on the IV drip firmer this time. This time, I can pull it along.
I run. Run back to the door. I had left it open. I run through it, across the dark room, and into the road.
What? No, I'm meant to be back in my room. No, no. I'm not meant to be here.
I look down. I'm not on the zebra-crossing.
Big Sister told me to always use the zebra-crossing.
Where is Big Sister?
Through blurry eyes, I see glaring lights. 
Big car. No, it's a truck. Car and truck is different.
It's rushing at me.
I'm frozen. I hug my IV drip. I can't see Big Sister. I want to go back to the white door.
I close my eyes.
It happens fast. 
Strong arms scoop me up, and into a sturdy chest. Shielding me from the big car. It's a truck.
I look up.
Big Sister.
There's red paint on her face. Her smile is pained, but happy. How can you be hurt and happy at the same time. 
'There you are.'
That's not paint.
That's not paint.
There's paint on me, too.
My IV drip is missing.
I feel hurt. It hurts bad.
But I'm also happy. I can see Big Sister now.
Oh, you can be happy and hurt at the same time.