Use this chart to find out if you are prepared to let go.
CHANGING A JOB
Wherever you go, some work-related problems will follow: stress, gossip and occasional work overloads. Don't change jobs because of these problems unless they simply won't go away and if the management does not address them even if you have brought their attention to them. If you get a good offer, make sure it is in harmony with your long-term goals. If you leave your job for a better pay-check only, you might end up regretting it.
STARTING YOUR OWN BUSINESS
You will never be absolutely ready. You can fail even if plan everything in detail. The least you can do: prepare a business plan and have it checked out by an expert. Make sure you have enough money and make a list of possible clients. Don't be unrealistically optimistic. Your business costs won't magically disappear just because you have a good idea.
TAKING A LONG BREAK
When you take a longer break, let's say a year-long, the worst part is that you are doing nothing for your career. So make a detailed plan and break it into smaller, well thought-through goals. Make sure you will be able to survive financially and don't forget about money for emergencies. Don't hesitate until the last moment to deliver the news to your employer so they have enough time to find a replacement for you. If you plan to return after your sabbatical talk to your employer if that is even possible.
Thinking about quitting your job to continue your education which will enhance your chances for a promotion in your current field or will enable you to have a career you want is the least risky option. Choose a quality educational establishment. It might be more expensive but your investment will be returned. Make sure that the educational programme is renowned and widely accepted.