I think it is a big decision to quit a day job and be full time working on Steemit. I think first of all, you have to ask yourself how much you are earning now versus how much you can earn from Steemit.
Based on my personal experience, it is not so easy to be noticed on Steemit and start getting those big votes. Your reputation and network will take at least half a year to build. And even after 6 months, I am still unable to get more than $1 of organic upvotes per post. So assuming if I post 2 articles a day, I will earning less than $60 per month. Which is far from enough to survive in my country.
Next, you have to consider how much you need to cash out from Steem to fiat every month. Steem is a platform which rewards people who hodl. The more Steem power you have, the larger your vote is. Hence, it makes sense to hold on to your Steem. However, by quitting your day job, you will certainly need to cash out whatever you earn to maintain your daily life.
There is an exception though. If you intend not just to write on steemit, but instead start a business on the Steem platform, then it maybe viable to take the leap of faith.
In conclusion, Steem can be a hobby and a nice source of side income. But it is very risky to quit your job and focus on Steem. I will recommend anyone who have such plans to think twice.