cry yourself to sleep: o que isso significa?

Have you ever been so sad that you cried until you fell asleep? There's an expression for that: Crying yourself to sleep. So imagine it's your birthday but nobody remembered it. At first you thought there would be a surprise so that's why everybody was acting so suspicious and quiet. But the day passed by and nobody came up to you to say a single "happy birthday". When it's time to go to bed, you're feeling miserable like the most unwanted person on the face of the planet. So you cry yourself to sleep. That means you cried so much you fell asleep. That's it for today guys. Take care!