The best advice that I ever got from another writer was from John Green, quoting Robert Frost, and it was “the only way out is through.”
In the context he was using the quote in I think that he intended it to mean that the only way to get out of writing a book was to finish the book. Once you get started on a book it’s going to be there for the rest of time regardless of whether you finish it or not. If you don’t finish it then it’s always going to be there taunting you saying, “you couldn’t finish me. You aren’t the writer you claim to be. You failed and I won!” It you do finish it then you’re done. You send it out into the world for other people to deal with. It’s no longer your problem.
However, at the time I read his quote I was having a bad week, so I saw it more as life advise. When everything’s flying at you all at once and it looks like there’s no way out all you can do is put your head down and plow through it. Even though you feel horrible at the time it’ll end up like every other situation. You’ll get through it and you’ll move on to the next chapter in your life.