Was working full-time in the ad industry and quit when my first one was 6 months old. Always thought of myself as a career person, but my priorities totally changed after having a baby. Starting Baby Signs Hong Kong has given me a good 'balance' in that I am still "working," but it's a job that allows me plenty of time with my family and it is also something that I LOVE doing and totally "relevant" at this particular stage in my life.
One thing I can say, though, is that when you start your own business, you need to be totally aware of the realities, the trade-offs (e.g. the investment money- and time-wise, etc.). Depending on what you want, what you're looking to achieve, what you end up with, it can be either very fulfilling and rewarding or frustrating. Have to go in with both eyes open. Good luck (and happy to answer questions if you PM me).