I will presume you mean that you can write and get paid for it, and could actually choose a life as a professional writer, without starving.
If that is the case (and this answer is tailored to your situation) your problems are quite similar to the problems of a free-lance "gig" programmer; a technical contractor. I have done that job. Or a self-employed programmer, I am aware of a few that write cheap phone apps (99 cents or $1.99) and were actually making a living doing that.
The problem with self-employment are getting gigs, money and time management. All are conquerable.
Trivial work expands to fill the time available. It's a law of nature. With a job and a boss, you don't have a choice but to show up nearly every day, and spend the day doing your damn job. You are compelled to be productive. Even if you love writing, it is extremely easy, when stuck, to turn on the TV and see what's happening in the world, or catch up on the laundry, or go ahead and put away the dishes. Or surf the net. A regular job has external drivers, people checking on your progress, people that need things, mandatory meetings and presentations.
All of that vanishing in a white mist is exactly what you want, but we quickly become accustomed to new and better things, and soon your enthusiasm fades. Part of your enthusiasm for writing all day was precisely the lifting of these imposed pains and strenuous work to meet unreasonable or irrational productivity demands, but six months in --- That is no longer motivating you. You have become used to that, and don't want to go back --- but you are also getting used to starting late and quitting early and taking two hours for lunch, and calling the rest your "thinking" time. If you want to be self-employed, take your job ethic and apply it from the start and do not waver. Get used to the lack of pain and external demands, do not get used to the freedom; treat it like a job.
That is, more or less, the advice of Orson Scott Card: Set your writing hours like a job, and during that time, sit and stare at the empty page or type. Your choice, but no other choice. Do nothing at all, or write. You can do research but don't surf or read for entertainment. Train by reading a book or blog on writing, fine. But make no "writing" excuse to read about the top ten celebrity cheaters, stick to the real job of writing.
For any self-employed start up, being stingy with money and expenses and as frugal as possible with credit is a survival skill. Stephen King counts 1500 of hours of writing to finish a novel; that is 9 months of full time work. (Less for him, he writes literally every day, weekends, birthdays and holidays included). He also has decades of practice writing publishable work; your hour count may be twice his.
In any case, income is uncertain in a gig economy, so until you have enough to survive on interest alone earned by your capital, conserve money like your future life depends on it. Because it does. For a beginning author, advances on books accepted for publication are in the $3000 to $5000 range. The majority of first books never pay another dime after the advance. $3000 for nine-months work? You can't live on $333 a month.
Maybe you can write a best seller. Don't count on it, if you are going to try it, have the resources to survive for three years on homemade sandwiches. And before you begin, make sure your resume is up to date and could get you a job if you fail.
I've been involved, as investor and/or worker, in over a dozen startups. 3/4 failed. The others have paid for those failures and more, but the number one cause of failure, IMO, is relentless optimism that leads to wasted resources (early overspending) and a failure to make any realistic plan for setbacks; because the relentless optimism just doesn't believe they will happen so they treat such planning as a formality in their business plan.
The number one cause of success is realistic pessimism leading to realistic contingency planning. What can go wrong? How will you know it went wrong? How fast can you know it? Is there any way to accelerate that failure into a time realm where you still have resources to address it?
The hardest part of this is trying to come up with definitive bright lines you will use to know when something bad has happened. Your advertising is not working well enough to cover expenses. Your online campaign is costing you $1 in clicks for every $0.10 in sales.
People hate this part of business planning, but you are not planning TO fail; you are planning to NOT fail if various unfortunate incidents befall you. Illness (yours or somebody else's). Or all your agent query letters go unanswered. Or they get answered but your manuscript is always rejected. Or you get terms quickly; how do you know if a scammer has found you?
Don't go into business until you know the mechanics of that business; and once you know the mechanics, put on your author's hat, become a villain, and try to see the attacks and frauds they could make to extract money (or rights) from naive authors and research that. Make a plan to NOT be victimized. Make a plan to deal with rejection. Make a plan to not run out of money before you have given this business a fair shot.