It depends on the current situation of your job. For me, i am focusing on both, for these reasons:

1. I am just entering the world of Bitcoin (so i am a total newbie)
2. My job is currently my primary source of income

But, if in the days / weeks to come, and i am able to find luck here in the bitcoin, then there is a huge possibility of quitting my job. But hey, it is also good to earn in another way, so more likely i will be focusing more on bitcoin, and having a job that requires less attention. Or if i could get lucky with the bitcoin, i will use it to start my own business. So to cut the long story short, here is the flow chart

BITCOIN -> gets lucky -> find a job that requires less attention -> start my own business.
BITCOIN -> gets unlucky -> stay with the job and study more about the bitcoin.