Sea

“An entire sea of water can’t sink a ship unless it gets inside the ship. Similarly, the negativity of the world can’t put you down unless you allow it to get inside you.”  ~Goi Nasu (via JulesOfNature)

I couldn't track down an original source for this quote; in fact, the only thing search engines could come up with for "Goi Nasu" was this quote.  That gives me pause.

But whoever said it, in whatever context, I still like it.