King of The Castle

Beating the other climbers easily to the top of the wall this little fella couldn't help but show off, taunting the slower ones below with songs and rhymes that popped into his head:
"I'm the king of the castle. I'm the king of the castle. Get down you dirty rascals..."
"I'm on the top of the world looking down on creation..."
"I'm A number 1, top of the heap..."
As he paused for breath he was sure that he could hear a voice above him singing:
"Humpty Dumpty sat on a wall. Humpty Dumpty had a great fall."
Hearing this voice he remembered an old saying his grandmother had repeated to him many times while he was still young. As he remembered his grandmother's voice he very quickly sat down in terrified silence to wait for the others to join him.
What was the old saying?  - Pride comes before a fall.