Who said "I don't know how I'll do it, but I will."?

This quote is attributed to Dory.

I don't know how I'll do it, but I will. - Dory

"I don't know how I'll do it, but I will."

Dory

"Just keep swimming, just keep swimming, what do we do? We swim, swim, swim!"

"I suffer from short-term memory loss."

"When life gets you down, you know what you gotta do? Just keep swimming."

"I'm sorry, what were we talking about?"