Hit the sack

[supada]

I found its definition in dictionary as "Prepare for sleep."

I wonder what kind of situation we should say this words? Normally I would just say "I'm going to bed." or so.

Please help me be clear with its usage. Also please correct any grammatical errors on post. : )

Thanks.

[David L.]

"I'm going to hit the sack' is colloquial for "I'm going to bed."