Setting goals for yourself as a writer is really important. My goal was to have the final draft of my book done by the end of September. I won't make that goal, and the reasons for that are entirely out of my hands.
The further you get into your process of writing, producing, and publishing a book, the more people you're going to need to get the job done. You'll email back and forth with artists, layout specialists, editors, beta readers, customer support, printers, and so on. I have a lot of great stories to tell, but since I'm in the middle of working with these good folks, I haven't had the benefit of reflection on how our interactions have proceeded. So, sadly, the stories will have to wait.
But what I can tell you now is that when you are dealing with so many different people (I've worked with people on three different continents so far to get my book done), it's inevitable that disaster will strike. And I do mean disaster. Family illness, hurricanes, traffic accidents, financial corruption, are just a few of the challenges the people you collaborate with will face. I like to call them "unlikely inevitabilities." The odds of one of these things happening to any individual in the world populace is infinitesimally small. However, they absolutely will happen to you when you're trying to produce your book, especially if you're trying to do it right.
So what can you learn from my experiences? One, treat others with respect. I'm going to write about treating your book as a business down the road, but people are frail and fragile, and we're all in this together. I know they promised you a thing by a certain deadline, but when their life is shattered, you have to be understanding.
Two, build in lots of time for each stage of your project. You absolutely must have margin for error, because errors are going to happen. I don't anticipate my book being out for another 5 months, but even then, I feel like I'm cutting it close (and I'm on the final draft). Emails can take days to get answered. Drawings might need to be revised. Covers aren't perfect on the first mockup. You have to allow humans to be human, to make mistakes and to have a chance to correct them.
Three, build a support team around yourself with people you really trust. You're going to freak out. You're going to worry. You're going to doubt yourself and doubt the intentions of the people you work with. In those times, you need someone to help keep you grounded - to remind you of your goals and your values. I can't stress this enough.
If you're writing, I wish you the best of luck. I hope my experiences can help, even if it's just a little. Stick with it. I believe in you :)