Surprisingly, it's no surprise,
To find the truth in all my lies,
When fast asleep with open eyes,
I'm breathless as I breathe.
I whisper, as I scream at you,
“I'm overjoyed at feeling blue,”
I'm joking, but I mean it too,
And enter as I leave.
What am I?
Hint:
Not an oxymoron or paradox, but similar.