A person can have a job he/she is doing and at the same time have an amazing business idea. Do you think it will be a great step to quit the job and go into the business? That is not advisable in any way. If you have conceived a good idea you can build on it while still holding down your job just to be on the safe side. You cannot say for sure whether the business will be successful at first or not, so you should not put all your eggs in one basket.