it doesn't get any easier. Of course, logic says it should, and because of this you remain optimistic that writing the next book will be a cake walk, that your ideas will flow through your fingers onto the page with such ease and clarity you'll soon be spinning out 2-3 novels per year!
Well, I'm currently writing my fourth novel and this magical shift still hasn't happened. However, I'm happy to report that other authors I know (some who've published ten or more novels) agree with me on this point: the process itself doesn't get any easier, though with each finished novel an author's growth inevitably shines through -- improvement in the writing, confidence on the page, style, structure, tone, etc.
So for those teenagers writing short stories for the competition I sponsored this spring... don't give up, and remember, the best writing is always done in the rewriting.