Shouldn't you already be in bed?
I can't sleep. I'm really not all that tired.
You need to get some rest, as you have to get up early in the morning.
It's impossible for me to get to sleep right now.
Just close your eyes, and try not to think.
That really does not work for me.
It doesn't matter, you need to get some sleep.
How about I tire myself out, and then fall asleep when I'm tired?
Then you're not going to go to sleep.
Don't worry, I'll make sure and get to sleep in a little while.
I want you in bed, right now, so sweet dreams.
Fine. Sleep well yourself.