There are two traps here: one is to over-outline and use that as an excuse to not get down to writing. The other is to blank page (also called “pantsing”, an expression, which, to me, means “lazy amateur who doesn’t care”) and then not know what to do next.
There is nothing wrong with either technique, unless it prevents you from doing the actual writing.
If you have tight deadlines or juggle multiple projects, I suggest that you outline. That way, you can sit down each day and have an idea of the day’s work, thereby meeting your quota. When you Blank Page, it’s very easy to sit down, be overtired or unfocused, say “I can’t”, get up and walk away. Do that for a few days, and you’ve blown your goal.
You’re not in competition with any one except yourself, but unfinished projects drain creative energy. In fact, I teach a class called “The Graveyard of Abandoned Projects”. Make the commitment to do this, fulfill the commitment during the month, go past it if you need to in order to finish, and THEN decide where you’ll take it.
Remember, you are under no obligation to ever publish this. So don’t look at it and think, “it sucks, no one will ever want it.” If you choose to keep working on future drafts, it will have a life beyond the first one. If you choose to stick it in a drawer and use what you learned on a different project, that’s fine. It’s your CHOICE. But make sure it’s a CHOICE and not a cop-out by not finishing.
If you decide to outline, it doesn’t need to be anything fancy. I do what I call a “Writer’s Rough”, which is basically a scene list with a sentence or two of description or dialogue about each scene. When I sit down to write, I fill it in. For me, that is the best of both worlds – I’ve got a framework, but I’ve got room to explore.
There’s also nothing wrong with keeping it all in your head, if you’re good at that. Sometimes, writing it down dilutes the creative pressure, and you need to build it in order to have the momentum to carry you through.
Don’t be afraid of tangents – the focus of a first draft is words on paper. You cut and shape in the next draft(s).