If your writing dreams are to be more than pleasant illusions, you simply cannot afford to wait around for the Muse to show up. The habits of writing must be trained, and that takes discipline---both to get any serious work done, and to increase the chances that inspiration will drop in. The point is to train your brain to transition into writing mode on a regular basis, so that writing becomes intentional rather than haphazard.
Most serious writers understand that scheduling is important. We all get the same 24 hours given to us every day, and priorities are quickly revealed by the use of that time. If you seriously want to do something, you don't find time for it; you make time for it by blocking it out on your schedule. Whether it's a daily, three-times-a-week, or weekly chunk of time that you decide to devote to writing, the point is that (barring legit interruptions from still higher priorities) you are engaged in the business of writing in some way, shape, or form, to the exclusion of other activities.
This isn't about becoming a slave to rigid scheduling; it's about establishing a useful habit that will help shape your thinking. It generally takes three to six weeks of consistent practice to get a habit going, but once you have done so, you will probably find your mind more readily slipping into the flow of writing when the appointed time comes around. And, should a flash of inspiration strike at some other time, you still have the option of getting the thoughts down as they come; just don't allow these random moments to substitute for your scheduled time. (For those moments when lightning strikes, I'd suggest keeping a good old-fashioned note pad and pen handy; the act of scribbling something down is a much better aid to memory than many people realize, aside from having the physical record of your thoughts.)
Just as important as making a designated space in your schedule for writing is having a designated physical space for the work. It is not necessary to have a fancy home office; a small writing nook or even the kitchen table will do if you're there with your laptop at your scheduled writing time and have arrangements made to keep distractions to a minimum. Again, the point is to surround yourself with cues that signal your brain that the business at hand is writing. That means that your writing spot should be reasonably comfortable (physical discomfort does not help concentration unless you're far more of an ascetic than I am), organized in whatever manner you find most effective, and NOT the place where you usually answer texts, play games, and scroll through news and social media. If you give your brain the chance to cue in on dopamine hits instead of writing, it will probably do exactly that because of the more immediate rewards involved. If at all possible, turn the smartphone off entirely or put it in another room and set it to silence all contacts save those from your nearest and dearest (who should know about your writing schedule and, one hopes, will refrain from disturbing you without good reason).
Setting apart dedicated time and space for writing doesn't guarantee that you will ever complete a book, a magazine article, a poem, or much of anything else. You still have to put in the effort and do the best you can within the constraints you have. But, as the saying is, failure to plan is planning to fail. By creating an environment in time and space in which writing becomes the expected thing to do, you are at least putting yourself into a mindset in which regular writing is not only possible but likely, and there's a good deal to be said for that.
Happy writing!