Repeat it to yourself if you worry. If you are staring at the blank screen, waiting to figure out what words come next. If you can't think of that perfect word you need just now.
If you worry, know you are not alone. Everyone worries. That it won't be good enough. That you won't finish. That you'll get sick or distracted or stranded on a desert island with nothing more to write with than a stick and the sand.
It will never be good enough if you don't start it. Or if you just let it go half way through. You will never be able to make it good enough if you don't finish your first draft and move on to editing. Here's a little trade secret: No matter how good you feel your first draft is? It's crap. It honestly doesn't matter who you are. Your first draft is crap. You make the book in the editing.
You will never know if you can finish in the 1 month time frame if you don't try. And hey, if you don't finish the first draft in that frame... you can finish it after! :) Also... if you don't manage to meet the official word count (50,000 words seems really big at first!!), just think of it this way. You did a lot, in a short amount of time. And that's something. :)
If you plan a little in advance to get a few hundred words ahead every day, and you get sick? You're covered. If you get distracted, unplug. Do a word sprint. Turn on music and don't let yourself stop writing until an entire album is done. You are in control of this. You control yourself. You control your word count. You don't have to let the words rule YOU.
Now, that desert island thing? Sucks to be you. Hope you have flares. ;)