As a professional artist when you sell a piece, yes it is a very exciting feeling that gets your adrenaline running and makes you think “I can do this for a living.” But the down part is that there is no knowing when or if you’ll sell another piece again. But until then be happy that you have a way to support yourself. Basically your day job is the whole reason you get to be an artist in the first place. If it weren’t for that you would be a starving artist living on the street.
Having a day job can be a way to fuel your artistic practice. If your day job gets to you then use your artistic talent as a way to escape from what you do everyday. I have read up on artists who have had their art careers launched by constantly producing work due to how much their day jobs got to them. It can be a great form of revenge towards what we spend our everyday lives doing, whether we’re getting paid for it or not.
I know someone who told me about a friend of his who made the biggest mistake of his life. He once had a solo show that sold out. It was a show of 10 pieces all selling for $10,000 each, that is $100,000 he made all together from the show. He was so blown away by that accomplishment that he took it as a sign that it was time to quit his job. But that just led to disaster. After a year he didn’t have enough money to put food on the table because he couldn’t sell any other paintings.
If you’re asking yourself when you think is the rite time to quit your job to pursue your art I think it is when I think it is when the sales are coming in regularly and it earning you enough to support yourself. But personally I think having a day job is more important.