Rejections Rejections - A new Q for the Chics

Its been a while since I've asked the Writer Chics a question. I generally tie my questions to things that are currently going on with me and things that I've wondered if other writers experience.

So my question is this, and really, any author could answer this, since every one experiences it: How do you stay motivated when you receive rejection letters?

New Question for the Chics

I know a lot of authors out there (whether they are new or experienced, published or unpublished) have bouts of frustration in this career - I mean, really, it can be nerve-wracking - and I think that this week's question for the Writer Chics will help a lot of people.
What is the hardest part about being an author and how do you keep going?