The phrase "just do it" comes to mind. Really, it comes down to making the time. When I'm writing, I try to have a dedicated daily word count. Say 2,000 words a day.
From there, I pick a time of day to write. My imagination is usually at top performance first thing in the morning. I set my alarm for 4 and usually manage to roll out of bed by 4:30. I make coffee, quiet my stomach with a breakfast burrito, and just write whatever comes to my head–forever trying to hit that 2,000 word goal by about 6AM when I have to get ready for big girl work. Sometimes the writing happens. Sometimes it doesn't. Either way, I have a new book in about 2-3 months.
1) For the love of all that is holy, DO NOT READ BACK THROUGH YOUR MANUSCRIPT WHILE STILL WRITING IT. You'll just delete the whole thing because you'll be dismayed by how terrible your imagination is.
2) Writing contests, like NaNoWriMo, can give you a real kick in the pants.
3) Seek help. Sure you can learn to do everything yourself, but that takes so much TIME. Throw some money at your problem and let an expert handle it. I've found everything from formatters to graphic designers on sites like Upwork. You won't make back the money for a while, especially if you go indie, but if your only goal is to publish, sites like this are a dream.
4) Invest in a software like Scrivner to organize the chaos that is your thoughts.
Best of luck! If you write a book, be sure to tell me about it.