Writing can be so up and down. One day you're writing at a mile a minute, feeling like the best, most prolific, inspired writer in the world. The next day you can sit down and feel like your brain is made of mud.
I keep remembering the quote I read - Real writers write even when they don't want to. That usually keeps me at the desk!
Publishing is even more up and down. One day you can be over the moon because you've had a book accepted. A week later you can be tearing your hair out because the contract is terrible and you have to grit your teeth and negotiate somehow. And then your book comes out and gets a bad review.
It always comes back to the writing, I guess. If you don't love the process, the creation, the high from having written something that just might be OK - if you only are waiting for fame and recognition and maybe money - maybe you should try something else.
That's what I tell myself on the downer days, anyway.
And I also tell myself - being a writer is about perseverance and craft and always trying to do better.
BTW, am reading the 3rd Travelling Pants novel (Ann Brashares) and loving it - more than the first two. She really gets the emotional stuff with her characters working so well.