Imagine a sports team scheduled for a playoff game. The team does all the pre-work and the getting ready for the big event through conditioning and hard play. Then on the day of the event their star player decides not to show up. That would be akin to your doing all your project research, developing an outline for content, gathering your materials together, and then deciding you were not in the mood to write your book or article.
Writing is not a glamorous activity. Like any job, there will be times when you want to “call in sick” and take the day off. That is okay, as long as you do not make that a habit and spend more days out sick than at work. In fact, it is a good thing to get out and take a break periodically in order to refresh mentally and physically. Just remember that if you do not write; the work will never get into print. By continually avoiding writing, you may even develop writers block and start to question your own ability or motivation to get the material done at all.
Identify or create a writing process and stick with it. Set up a schedule for writing and stick with it unless a true emergency arises. Honor your circadian rhythm and you will likely increase your productivity. If you are a morning person and have more energy and mental focus in the early part of the day, write then. On the other hand, if your energy level peaks later in the day, select that time period for your creative efforts. Whatever works best for you, identify it and stay with it. Pretty soon, you will find the words flowing onto paper as you exercise your brain and paint images or create useful strategies in words.
Once you are ready to market your book(s), create a written plan of what activities you plan to conduct, dates when you will do them, resources required, other people who might be involved, costs, and any other factor you can think of. If you are good at developing spreadsheets, create one with these headings and track your efforts daily, weekly, and monthly. This provides a visual record of your progress, helps identify gaps, and can serve as a motivator as you see progress made. The key is to do something every day to brand and market yourself and your books. Otherwise, your revenue will not increase.