What does the quote, "Sometimes, I guess there's just not enough rocks." mean??

Question

it was in the movie Forrest Gump... help! :)

Answer 1

No matter how many rocks she throws at the abandoned house her father abused her in, there is no way to get back at him or change what happened.

Answer 2

Forrest and Jenny visit Jenny's now abandoned childhood home and she starts hurling rocks at it....cursing her abusive father....and then collapses into sobs.  

As Forrest goes to comfort her, his voiceover says "Sometimes, I guess there's just not enough rocks"

....meaning that there weren't enough rocks for Jenny to throw to alleviate all the pain from her father's abuse.

I think that people now use it to describe a (usually negative) feeling or situation so immense that they don't know what to do with it.