For me, I often try to set aside a certain amount of time I will be writing instead of a word-count (If you are a writer you will become familiar with word-count. 80k for a novel, 50k for a young adult novel, 20k novelette, 6k for a short story, 120-300k for an epic. The numbers are pretty fluid, but as a writer you'll probably become familiar with those numbers. I'll do another post on length another day.) Man was that ever a long parenthetical. Anyway, like I said, I usually tend to set aside a certain amount of time each day to write and any writing will work. However, if I am on a project I will change my goal to match the number of words per day I need to finish my project on time.
That brings me to my main point. Writing needs to be taken seriously, and it's not always easy. Most successfully published authors that I've talked to or listened to describe their writing as a job.** They sit down for a certain amount of time each day (just like a job) and work on writing. If they are making business decisions then they usually spend some time doing that too. But the biggest part of being a writer is writing. Your words are your product. Imagine if Nabisco suddenly stopped making Oreo cookies. First of all, the world as we know it would cease to exist. But second, they wouldn't sell any more Oreos. We would not be able to buy Oreos because there would be none. That's the same thing with your words as a writer. If you don't produce any, there won't be any...no matter how many good ideas you have.
An important mental shift for any writer is when they decide to make writing a priority-making it a job. Take some time to figure out what your goals are, and above all, write every day. Publishing a book is akin to getting a master's degree when it comes to the amount of effort you need to put in, and just like a master's degree, you don't usually get paid for writing along the way. Keep working, keep honing your craft, keep learning how you can best express your ideas and I'll see you on the other side...the published author side.
**One notable exception is Orson Scott Card who, when asked if he sat down to write every day responded with something like "No. That sounds too much like work." Though he did mention that when he's writing a project he will average about 4 hours in the morning and 4 hours in the afternoon...hmmm that sounds suspiciously like a job after all.