...takes time. Everything about the filmmaking process. No, scratch that, the creative process, takes time. From ideas forming into something more than just merely ideas. Now your idea is an outline of some sort. A conversation you can have with another person about it. The more time, the more something becomes an actual thing. And when you have that, you are ready to share it with others (finally, right!).
But books take time to write. And films can take years to make. If you think it might take a day, it will at least take a month ( just in my experience). That's just the nature of the process of perfection (or something really, really good). So don't let the time taking make you pull your hair out. Trust me, it'll fall out or turn grey with you stressing over your project anyway, so save the strands you've got.
But enjoy the hell out of it. Even the stressful parts (you're like, whaat?) Yes, those moments of stress, will be the moments you look back on, when you're writing your award winning speech for a nomination that you didn't even see coming!
In filmmaking, (especially depending on how big your crew is) time is a big factor. You want your project to be it's best. And unless your budget is unlimited, you may have a longer process to get your project done. Maybe it takes more time for scoring or editing. Maybe other things are a factor like actors availability or how the weather is in your location during a certain time of year. Fact is, what you might think (hope) takes a certain amount of time, could take you two Christmases... I know... I know (Stress! Aahh! - Hair!). But that's the process. However, by the end of it all, you should be able to present the world your baby, all shiny and new and worth all the near heart attacks you experienced!
Hang in there kid, you may have a long ride. Just sit back, kick up your Yeezy's and try not to go grey.